Mustard Allergy; The Neglected Stepchild of the Big 14

A spoonful of relish containing white and brown mustard seeds, 2 of the 3 types that can cause allergic reactions

Mustard has been a popular accompaniment to meat dishes for centuries and is now increasingly being used as an ingredient in all kinds of processed foods. So far, only IgE-mediated reactions to mustard have been reported, but they can be quite severe. People can develop food allergy symptoms after eating the seeds or leaves of the mustard plant, and rashes have been reported after using massage oils and alternative medicines containing mustard. The mustard-allergic should also be aware that mustard can be found in drinks and in cosmetics.

Fast facts on mustard allergy

Mustard allergy is quite rare and the studies examining its prevalence all come from France, the largest European consumer, where mustard is the 5^th most common food allergen affecting children.

The mustard-allergic may be allergic to other vegetables in the Brassicaceae family, such as cabbage, cauliflower, broccoli. They are more likely to experience cross-reactions to mugwort pollen, hence the existence of ‘Mugwort-mustard allergy syndrome’.

Mustard causes immediate, IgE-mediated reactions, and reports of anaphylaxis are relatively common.

IgE-mediated mustard allergy can be provisionally diagnosed with skin and blood tests, but only a food challenge provides an unequivocal diagnosis.

As mustard allergens tend to be resistant to heating and digestion, currently the only way to manage mustard allergy is to avoid mustard-containing food.

And now for the details, which include:

Table Of Contents

Mustard Allergy; The Neglected Stepchild of the Big 14

What is an allergy to mustard?

The mustard plant is indigenous to China and Asia and is the world’s most important spice crop. The first known use of mustard dates back to 3000 BCE. It evolved from wild weeds that grew in Asia and was primarily used as a condiment for meats, not so much to enhance their taste but rather to disguise it, as fridges and freezers had not yet been invented and the meat was often somewhat rancid.

According to historical record, the ancient Greeks and Romans were two of the first societies to use mustard as medicine. The seeds were crushed and made into an ointment and used to soothe sore muscles. By the time the Middle Ages arrived, mustard was primarily being used to add flavour to meals, but it was still being used in a medicinal capacity to treat gout and thin blood, and as an ‘effective cure for hysterical women.’

The name ‘mustard’ is thought to be derived from the Latin mustum-ardens. Ground mustard seed was normally added to ‘must’—unfermented grape juice—and the Latin for ‘to burn’ is ‘ardere’; hence ‘burning must’. Over time, this became ‘mustard’.

Mustard seeds are part of the Brassicaceae (formerly Cruciferae) family, which also includes broccoli, cauliflower, cabbage, Brussel sprouts, turnip and rape.

There are three major types of mustard seed used in cooking and food processing:

white/yellow (Sinapis alba / Brassica hirta)
brown (Brassica juncea or Indian/oriental mustard)
black (Brassica nigra).

White mustard seeds are much larger than the other varieties and a lot less pungent. They are the most popular seeds in Western cuisine. Several different varieties of mustard are made using these seeds, such as American-style yellow mustard, which is made from white seeds blended with vinegar and spices and often coloured with turmeric. The seeds are also used for making pickled gherkins, mixed pickles and sausages.

Brown mustard is grown all over the world and used mainly as a condiment in North America and Europe and for oil production in the Indian subcontinent. The leaves, stems, roots and sprouted seeds are eaten in hot and cold in dishes made in Asian countries like China and Japan.

Brown mustard seeds are the main ingredient in European- and Chinese-style mustards and white and brown seeds are blended to make English-style mustard. The traditional Dijon mustard, from the French city of Dijon, is made from brown or black mustard seeds blended with wine (vinegar) and/or verjuice and seasoning.

German mustard is produced by adding vinegar to a mixture of ground black and white mustard seeds. However, black mustard seeds are difficult to harvest in Europe and America and are more often used in Indian cooking. Oil made from black mustard seeds is used to make soap and for medicinal remedies. The plant also plays an important role in traditional medicine.

According to 2021 data, Canada is the world’s largest exporter of mustard, followed by Russia, Germany and India, and the biggest importers are the US (white mustard), Germany and France (brown mustard). The biggest producer of mustard is actually Nepal, but they keep their crops for themselves.

There is also a growing interest in using components of mustard—such as proteins or oils—in pharmaceutical and industrial applications.

Mustard seeds have a high oil (28 to 42%) and protein content (25 to 40%) which varies per mustard seed type.

Unfortunately, mustard can cause allergic reactions in a small percentage people. This happens because their body’s immune system mistakes one or more harmless mustard proteins for toxic invaders and creates IgE antibodies against them. The next time they eat mustard, the antibodies recognise the proteins and prompt a response from immune system cells. These, in turn, release a variety of chemicals into the bloodstream, including histamine, the chemical that is primarily responsible for the symptoms of allergy.

Worryingly for those people, mustard is increasingly being used in ready meals and other processed and pre-packaged foods, either to add flavour to meals or as an emulsifier, stabiliser or water binding agent for texture control in foods like processed meat, making it an important ‘hidden allergen’, especially in countries that do not require it to be put on the label.

Identified allergens

The proteins (and occasionally carbohydrates) in a food that are capable of provoking allergic reactions are called allergens. Allergens are named using the first three letters of the genus—Sinapis or Brassica—the first letter of the species—alba or juncea—and a number reflecting the order in which they were identified.

As of March 2026, 5 mustard allergens have been added to the WHO/IUIS allergen database (the official, peer-reviewed database of allergens maintained by the World Health Organisation and International Union of Immunological Societies):

Nerdy Data Alert! Open for TMI

Allergen	Type	Properties
Sin a 1	2S albumin, a seed storage protein	A major allergen* in white mustard. Resistant to heating and digestion.
Sin a 2	11S globulin	A major allergen in white mustard. May be used to predict the severity of allergic reactions. Shows cross-reactivity with tree nuts and peanuts.
Sin a 3	Lipid transfer protein (LTP)	Resistant to heating and digestion. Potentially cross-reactive with other LTP foods such as peaches and mugwort pollen.
Sin a 4	Profilin protein	A minor allergen in white mustard. Vulnerable to heating and digestion. Cross-reactive with other profilin foods such as melon. Involved in pollen food allergies.
Bra j 1	2S albumin, a seed storage protein	A major allergen in oriental mustard. Similar in structure to Sin 1 a, so people who are sensitised to white mustard are likely to be sensitised to oriental mustard and vice versa.

*An allergen is considered a ‘major allergen’ if over 50% of sensitised people produce specific IgE towards it. A secondary or ‘minor’ allergen causes fewer sensitised people to produce specific IgE towards it and is often (but not always) associated with less severe allergic reactions.

The percentage of subjects who react to an allergen can vary widely between studies, depending on:

the population being studied (where they come from, their eating culture, whether they have another allergic condition e like e.g. eczema)
whether the tests are being done on live people (‘in vivo’) or carried out in test tubes (‘in vitro’) using the blood of people known to be allergic
the food being used, which can contain different mixes and concentrations of proteins—if, indeed, a whole food is being used at all. Some in vitro studies can use just a single protein or even individual protein subunits
the methods being used to determine sensitisation or allergy (a food challenge is the ‘gold standard’ of testing and more accurate than a basophil activation test which is more accurate than a skin prick test, for example)

This can lead to a lack of consensus within the scientific community on which allergens in a certain food are immunodominant (stimulate the average person’s immune system more than others) and should therefore be considered major allergens.

What’s more, people can be sensitised to more than one type of allergen. They also tend to react in their own way to different allergens, so whether a trigger food is going to be a major problem for someone is ultimately a personal thing.

Other types of allergens such as oleosins and enzymes exist in mustard, but they have yet to be named, fully characterised and added to the official WHO/IUIS list.

You can find more details on these allergens and others in Allergome, a vast, non peer-reviewed database with the most extensive information on allergens on the web. It includes all the allergens that have been identified and characterised in studies, including those not listed inn the WHO/IUIS allergen database.

View from above of one red wooden figurine of a person standing between a group of blue ones on a white surface.

How common is mustard allergy?

A definitive diagnosis of allergy can currently only be established with a food challenge, but challenges are costly in terms of both time and resources, as well as potentially risky. So many prevalence studies measure sensitisation—using skin or blood test data—but sensitisation is not allergy. Being sensitised to something simply means that your immune system recognises it, but you may not actually react to it; in fact, many people don’t react to whatever it is they are sensitised to. Studies that use sensitisation data therefore tend to produce allergy prevalence numbers that are larger than they should be.

LINK TO CONTROL_Oral Food Challenge PAGE

In a similar vein, studies that estimate allergy prevalence using questionnaires usually produce somewhat inflated numbers as people can self-report allergies that they do not actually have, although robust studies will use certain criteria to evaluate respondents’ answers and determine whether their symptoms suggest an allergy or not.

IgE-mediated allergy

France is Europe’s biggest producer and consumer of mustard and also the country to turn to if you want any kind of data on the prevalence of mustard allergy.

Mustard allergy seems to be the most common allergy among spices.

A retrospective analysis conducted in 1994 to look into which foods were most frequently associated with anaphylactic reaction over a 9-year period (1984–1992) at a hospital in Lyon found that mustard was associated with 3% of anaphylactic reactions in 580 patients.

Mustard allergy has been reported to account for 1.1% of food allergies in French children. However, the prevalence of mustard allergy seems to vary according to the eating habits of the people in the region; thus around 1% of food allergies are due to mustard in the East France, about 3% in the centre of the country and about 9% in the South.

Because allergic reactions to mustard seem to start so early in life, it has been suggested that sensitisation may take place through breastfeeding or even in utero, before the baby is born. The presence of mustard in some baby foods only helps to increase the chances of early sensitisation.

The prevalence of mustard allergy appears to vary according to the eating habits of the people in the region; thus around 1% of food allergies are due to mustard in the East France, about 3% in the centre of the country and about 9% in the South.

The proportion of allergic reactions caused by mustard (in French children) has apparently been falling in recent years. Studies carried out in 1997 and 1998 determined that mustard was the third most common food allergen affecting children in France, behind egg and peanut. Then studies carried out in 1999 and 2002 determined that it was the fourth most common food allergen, this time behind peanut, egg and cow’s milk, and a 2013 study put it in 5^th position, behind peanut, egg, cow’s milk and tree nuts.

Despite this slip in the ‘most problematic allergen’ rankings, researchers have also noted an increase in sensitisation to mustard over the years.

Close-up of broccoli, cabbage and cauliflower at a food stall.

Cross reactions to mustard

Technically-speaking, a person can be allergic to mustardand another food (or foods, or aeroallergen(s)) either by cross-reactivity—the immune system mistakes the proteinin one allergen for aprotein with a similar structure in the other—or by an independent sensitisation to each food and/or aeroallergen(a co-sensitisation or co-allergy), in which case the immune system has developed specific IgE antibodies against each allergen. It can be difficult to determine whether reactions are caused by cross-reactions or co-allergies,but the end result is the same; problems, problems.

Because of structural similarities between the allergens in different types of mustard, people who are sensitised to one type are likely to be sensitised to other types, too. In one study, for example, a patient who lived next to a mustard seasoning factory which emitted ‘an unpleasant smell’ became sensitised to two species of mustard—black mustard (B. nigra) and brown mustard (B. juncea).

Lab studies have found that people with mustard allergy have a theoretically high risk of being sensitised to rapeseed (aka oilseed rape, also in the Brassicaceae family), because of a high structural similarity between the principal rapeseed allergen and the principal mustard allergen Sin a 1. However, although a cross-reactive allergic reaction is theoretically possible, there have been no reports of cases involving any mustard-allergic patients actually having a reaction to rapeseed.

There has, however, been a study showing that French and Finnish children with eczema who are sensitised to mustard, turnip rape (also in the Brassicaceae family) and rapeseed do react to turnip rape.

People who are allergic to mustard are likely to be allergic to vegetables in the Brassicaceae family—such as cabbage, cauliflower, broccoli.

They may also be allergic to fruit—particularly those in the Rosaceae family, such as peach, apple, pear, apricot, plum, cherries, and strawberries—andnuts, including almonds, also in the Rosaceae family. Test tubes studies have shown that certain mustard proteins share structural similarities with proteins found in Brazil nut as well as proteins found in hazelnut, pistachio, walnut and peanut, which could help to explain cross-reactions between mustard and these nuts.

One study has also reported some mustard-allergic patients who reacted to corn, and another study has found potential cross-reactivity between some allergens in mustard and wheat and sesame.

People who are allergic to mustard are also often allergic to pollen, as demonstrated by this Indian study, in which almost a quarter of the subjects were allergic to one or more types of mustard pollen, and this French study in which every child who tested positive to one or more spices, including mustard, was also allergic to grass pollen, and 3% were allergic to birch pollen.

But by far the biggest problem for the mustard-allergic is mugwort pollen. In fact, it’s such a common problem it has its own name: Mugwort-mustard allergy syndrome. It was coined in 2005 by Spanish researchers, who were surprised to find that 37 of their 38 mustard-allergic adult patients were also allergic to mugwort.

This syndrome can produce surprise results, as in the case of a previously non-allergic 73-year-old Japanese man who developed an allergy to mugwort and then became allergic to mustard and, eventually, ended up in hospital with facial swelling and shortness of breath after eating a bowl of boiled broccoli.

A green heartbeat trace on an ECG monitor

Symptoms of mustard allergy

Immediate reactions to mustard

Immediate allergic reactions are caused by IgE antibodies. These antibodies bind to certain immune system cells—mast cells and basophils—and trigger the release of histamine and other inflammatory chemicals that cause the characteristic symptoms of allergy.

Immediate reactions are the only type of allergic reaction that have been reported to mustard (so far).

Reactions are different for different people, and they can also be different for the same person, varying in severity from episode to episode. They can be classified according to the organs they affect and include:

Skin symptoms: eczema (atopic dermatitis), hives (urticaria), swelling of the face (angio-oedema) and/or tongue and/or throat and/or hands, redness (erythema), itchy skin (pruritus), oral allergy syndrome (OAS, commonly manifesting as ‘itchy’ or ‘burning’ symptoms often limited to the mouth, sometimes also swollen lips and cheeks)
Breathing symptoms: blocked nose (nasal congestion), runny nose (allergic rhinitis), wheezing, difficulty breathing/shortness of breath (dyspnoea), persistent cough, hoarse voice
Digestive (GI) symptoms: nausea, diarrhoea, vomiting, stomach pain
Cardiovascular symptoms: low blood pressure (hypotension), rapid heart rate (tachycardia), loss of consciousness (syncope)
Neurological symptoms: headaches, dizziness, blurred vision, anxiety, confusion, seizures, fatigue and malaise (aka ‘a feeling of impending doom’, which can occur during anaphylactic reactions)

Mustard produces a whole range of symptoms, from mild ones like Oral Allergy Syndrome, hives, red, itchy eyes, allergic contact rashes and allergic rhinitis (hay fever), to more serious ones like asthma, throat tightness and digestive symptoms.

Anaphylactic attacks are not uncommon and cases have been reported after eating hamburger with mustard, sausages with mustard, vegetable sandwiches and salad containing mustard, a quinoa dish containing mustard seeds, pizza, chicken dips, mustard mayonnaise and small amounts of mustard sauce.

These kinds of examples are frequent enough that, over the years, several different researchers have suggested that, when a patient has an anaphylactic reaction to an unknown allergen, they should be tested for an allergy to mustard.

The risk of having a severe allergic reaction appears to be higher in adults than it is in children. Clinical studies have found that children are more likely to have mild symptoms like eczema, skin rashes and oral allergy syndrome. And, whereas various studies on general food allergy carried out in France have reported anaphylactic reactions in about 2% of children allergic to mustard, research in adults puts that number somewhere between 10% and 48%.

Don’t panic: To be clear, the official definition of anaphylaxis is probably not what you think it is.

According to the medical definition, anaphylaxis is a severe, generalised (affecting the whole body) and rapidly evolving allergic reaction with symptoms that involve two or more organ systems (skin and/or airways and/or digestive system and/or cardiovascular system).

There are several grades of allergic reaction, the last 2 or 3 (depending on the definition being used) of which are classified as ‘anaphylaxis’. You should not think of these as being fixed or necessarily recognisable stages; a person can go through each grade very fast or even skip one or two completely. Most people suffering from a serious allergic reaction will not get past the lowest grade of anaphylaxis before their symptoms resolve, especially if they get proper treatment—i.e. adrenaline.

What people often think of when they hear the term ‘anaphylaxis’ is anaphylactic shock; a medical emergency involving a dangerous drop in blood pressure—by at least 30%—which can manifest as difficulty breathing and/or fainting. Anaphylactic shock is the most severe form (Grade 4 or 5) of an allergic reaction and is extremely rare.

This means that many of the cases of anaphylaxis reported in medical studies are not actually life-threatening—when dealing with an emergency, however, since it’s impossible to predict which reactions will become life-threatening, every case of anaphylaxis should be treated as if it is potentially deadly.

Mustard has also been reported to cause other types of severe symptoms, including acute pancreatitis, a sudden inflammation of the pancreas which generally manifests as stomach pain and can normally be treated with no lasting damage.

Because symptoms can be severe, if you do suspect that you’re allergic to celery, it’s important that you see your GP/family doctor and get a referral to an allergy clinic for further testing.

Threshold for reactions

VITAL®, the Australian initiative for voluntary incidental trace allergen labelling, put outrecalculated threshold doses for the ‘Big 14’ allergenic foods in 2020. Using a database containing datasets from studies carried out worldwide that used double-blind, placebo-controlled food challenges (DBPCFC), they calculated that the lowest threshold dose of protein that was needed to produce a reaction in 1% of the population allergic to mustard is 0.07 mg. (Note: in this case, the ‘population allergic to mustard’ is 33 people who were given a DBPCFC)

This is one of the lowest eliciting doses of the main allergenic foods. 1.1 mg was the dose needed to produce a response in 10% of the test subjects, and 17.2 mg was the dose needed to provoke a reaction in half of the test subjects.

Note: we’re talking about milligrams of mustard protein. (Bearing in mind that different types of mustard seeds contain different amounts of protein) if a teaspoon/packet of yellow mustard contains about 0.2g of protein, or 200 mg, someone who reacts to 0.07 mg would only need to about a 3 thousandth (200/0.07 = 2,857) of that teaspoon’s worth of mustard to react.

In one case report, a patient had an anaphylactic reaction after dipping her chicken in a ready-made dip. The researcher estimated the concentration of the offending spice as being 0.15 mg of mustard in 100 mg of dip. Another case reported a reaction to the mustard glaze on some ham. In one case, the smell of mustard was enough to provoke a reaction.

Ultimately, the threshold dose needed to provoke symptoms varies widely between people. It also varies per person, depending on the circumstances around the meal.

Your threshold can be lowered and your allergic reactions worsened by things called ‘cofactors’. Cofactors include things like how much you eat and whether those ingredients have been cooked or processed, as well as exercise, anti-inflammatory drugs, alcohol, infection and stress.

Mustard has been specifically implicated in cases of food-dependent exercise-induced anaphylaxis (FDEIA).

Cofactors are thought to play a role in about 14% to 30% of all anaphylactic reactions.

Please note: the amount of mustard needed to provoke a reaction says nothing about how severe the reaction will be. And, even if your reactions have been mild in the past, that does not mean that they will continue to be mild.

A close-up view of the mid-section of a man in a white coat with a stethoscope around his neck writing some notes on paper in a slim ring binder.

Diagnosing mustard allergy

A diagnosis of mustard allergy will primarily be based on your clinical history—a record of consistent symptoms following the consumption of mustard or mustard-containing foods. This will require you to provide your allergist with answers to questions about your general medical background (including any other allergies you may have and relevant illnesses in your family) and your dietary history (what you ate to provoke your symptoms, what those symptoms were, how long they lasted, whether you had exercised or taken painkillers and many other details).

Your medical history determines what comes next; on the basis of your answers, the allergist will try to determine what type of allergy you have—a primary, immediate-type allergy, a cross-reactive allergy or a delayed-type allergy—or whether it could be something else, and this will determine the tests they ask for to come up with a diagnosis.

Diagnosing immediate reactions to mustard

Skin tests

An IgE-mediated sensitisation to mustard is typically confirmed by a skin prick test, which involves someone placing a small sample of mustard extract onto your skin (generally the forearm of an adult/older child or the upper back of a young child) and pushing it through the top layer of skin by pricking it with a lancet. It takes about 15 minutes to see a reaction (or not).

This test is often carried out first because it is quick and simple to perform and gives rapid results, but it is generally used to rule out an allergy rather than to confirm one, because it has excellent negative predictive value—if the skin weal is under a certain size, you are highly unlikely to have an allergy—but poor positive predictive value—the skin weal has to be very large before an allergist can say with any kind of confidence that you probably have an allergy.

The accuracy of the skin prick test can be limited by the fact that the processing of commercially-made allergen extracts can destroy the heat-sensitive allergens, often those which people with a suspected pollen-associated food allergy react to. In such cases, someone could get a false negative result and be wrongly told that they are not allergic to mustard.

One solution to this problem is the prick to prick test. This test is very similar to the skin prick test, except first the lancet is used to puncture fresh food and then it is used to prick your skin. When the food is in liquid form, the technique is actually the same as the one used for the skin prick test and, when the food is solid, it’s often ground down and put in saline solution.

The prick to prick test often produces superior results to commercial extracts because the fresh food used should contain all of the allergens that a person can react to. The lab used by the clinic can also prepare the extract in specific ways which may add to its efficacy.

A skin prick test can produce a false positive result because of irritating substances contained in mustard—like capsaicin—which can trigger symptoms that look like allergic reactions.

Blood tests

Sometimes, the doctor may decide to order a blood test, aka an immunoassay. Perhaps the skin prick test was inconclusive, or the suspected allergen is not available for skin prick testing, or you’re unable to undergo the test for some reason.

A blood test involves having a small sample of blood drawn so that it can be sent to a lab where technicians will use allergen extracts to check whether there are IgE antibodies in your blood that react to them. It can take 1 or 2 weeks to get the results.

Blood tests can be less sensitive or specific than skin tests, but they have other advantages: they are perfect for people who cannot stop taking certain medications or have extensive skin disease or tattoos, and they can safely be used on infants, squirming toddlers and people who are at risk of suffering an anaphylactic reaction.

Blood test panels also typically include a whole range of potential allergen extracts including other foods or aeroallergens that the allergist may want to check your reaction to.

For more specific information, a component blood test—aka Component Resolved Diagnosis (CRD)—can be carried out. Instead of using extracts of whole foods containing only (heat-stable, plentiful) allergens, the CRD tests the reaction of IgE antibodies in your blood to isolated, individual proteins. This improves the diagnostic sensitivity of the test as allergens that would otherwise be missing from the whole lupin extract or exist only in tiny amounts are present in concentrated form in the CRD test.

This type of test enables the doctor to see exactly which allergen(s) you react to, which allows them to determine whether you are sensitised to cross-reactive allergens that are unlikely to produce symptoms, and whether you are sensitised to certain allergens that could affect your management plan. For example, if you’re sensitised to Sin a 3, you may also be sensitised to peaches and/or mugwort pollen.

Component blood tests are also made up of very large panels of allergens which include many other foods and aerollergens that the allergist may want to check your reaction to and can help to determine whether or not a sensitisation to a cross-reactive allergen will be symptomatic or not.

Unfortunately, although CRD could potentially reduce the need for oral food challenges and contribute to tailored management plans, it’s not yet considered a routine diagnostic method and it’s not comprehensive; the most widely used tests neither contain all of the identified allergens (which are also not all of the possible allergens), nor are they universally available. Testing for certain specific mustard allergens would require special preparation and is therefore only likely to be done for research purposes.

Additionally, as it is with skin and standard blood tests, CRD is better at confirming an allergy than at eliminating the possibility of one. And, because sensitisation patterns differ according to geography and populations, with different allergens being more important in different regions and in people of different ages, allergists need to understand their patient populations so that they interpret the results of the tests correctly.

A positive skin or blood test does not mean that you are allergic to something. While skin prick tests and blood tests help with diagnosis, positive results only show sensitisation to specific allergens. Being sensitised to a food doesn’t mean that you’re allergic to it and that you will develop any symptoms.

For example, when 36 children with positive skin prick tests to mustard were given a food challenge in one study, only 15 of them had allergic reactions. In another study involving 30 people who had all had positive skin prick tests to mustard seeds, mustard flour, mustard seasoning or mustard extract, only 7 of them actually developed symptoms after a food challenge.

A positive test result simply means that your immune system is specifically aware of an allergen or allergens in that food. Why some people later develop an allergy to that food, and some do not, is not yet known.

Neither can the results of your blood or skin test predict how severe your reaction to eating some mustard might be; a large skin weal or high level of IgE in your blood do not mean that you will have a serious allergic reaction if you accidentally eat a sandwich with some mustard hidden it.

Food challenge

The only way to get a definitive diagnosis of mustard allergy, and to have some idea of how severe your reactions may be and how much mustard is needed to provoke them, is to undergo an oral food challenge. This generally involves eating a very small amount of mustard, waiting for a reaction, and then doing it again, gradually increasing the dose until an objective—visible—reaction occurs or a maximum dosage is reached. It can take around 4 hours, depending on the type of challenge undertaken and the length of observation time needed.

You can read more about oral food challenges here.

Oral food challenges can be undertaken to confirm the results of a skin or blood test but they are normally carried out either when someone’s history and their test results disagree (i.e. they have negative tests results but their history strongly suggests an allergy, or vice versa) or to check whether someone has outgrown their allergy to ensure that they don’t unnecessarily restrict their diet or worry about hidden allergens in processed foods.

Because of the risk of severe reactions, oral food challenges should only be done by an experienced consultant in a medical setting.

Practically speaking, most people do not undergo this kind of test since it requires a lot of time and resources. And oral challenges are rarely, if ever, offered to people whose history includes severe reactions to a suspected food. Whenever possible, allergy diagnoses are based on a combination of medical history and lab tests.

Although food challenges help to diagnose food allergies and identify a suspect food, there are other reasons to undergo food challenges, namely:

to identify culprit foods in cases of allergies to multiple unknown foods
to determine a patient’s threshold—how much celery they can eat without reacting—so that dietary advice based on the outcome of the challenge can be given
to confirm the development of tolerance to celery

In cases where someone has a negative test result to mustard but their dietary history shows that they tend to have symptoms shortly after eating mustard, an alternative diagnosis of intolerance to sulphites is a strong possibility because sulphites are often included in mustard seasoning.

A mustard seed relish hides in a delicious-looking sandwich

Managing mustard allergy

Mustard allergens are resistant to both heating and digestion and they are not greatly affected by food processing.

Avoidance

Currently, the only treatment for mustard allergy is a mustard-free diet.

Reading labels

Manufacturers in the European Union/the UK/Canada are required to list mustard on the ingredients label of all pre-packaged foods.

Allergens can be highlighted in different ways on the ingredients labels:

They can be bolded, italicised, CAPITALISED, highlighted and/or underlined
They can appear in brackets behind an ingredient, e.g. Rayo (Mustard)
They can appear in a statement under the ingredients list, e.g. Contains: Mustard

For allergen labelling requirements elsewhere in the world, see the FARRP (Food Allergen Research and Resource Program) chart.

Food that is sold loosely, such as cakes in a bakery, should either have major allergen information displayed next to it or someone at the establishment should be able to provide you with allergen information if you ask them about it. That said, shop assistants do not normally see the food being prepared and they may not realise that a filled croissant, for example, contains mustard; i.e. their guess is as good as yours. So, if you’re not sure that they know what they’re talking about, it may be best to avoid foods that do not come with a list of ingredients.

Sometimes, food products can contain trace allergens—small amounts of allergens present in the food by accident, not as an intentional ingredient—because of cross-contamination during the processing stage. Although Good Manufacturing Practices are legally required to reduce this risk, it’s still impossible to guarantee that there will be no cross-contamination.

Businesses can use advisory labelling with a ‘May contain traces of…’ statement (or some version thereof, such as ‘Not suitable for someone with an allergy to…’ or ‘Processed in a facility that manufactures …’) to warn people of any allergens that may be present in their food. This is called ‘precautionary allergen labelling’ (PAL). It’s currently voluntary and there is no legal or practical framework governing the labelling. There’s no standard type of label, no threshold levels for allergens, and no way of detecting certain allergens at very low levels. As a result, this type of labelling can be haphazard and confusing, and the absence of a label also does not guarantee that a food is safe.

Unfortunately, for people with a history of severe reactions, there’s only one thing to do: when in doubt, don’t eat it.

There are, of course, apps to help you with that. Some of the ones that include mustard are:

AllergenInside (for Android and iPhone); scans barcodes and can translate product ingredients in over 40 languages. Also (3) sends you allergy recall alerts and hot news from the world of allergology
ShopWell (for Android); allows you create your own food profile and list the foods you need to avoid. It then scans product barcodes of items and simplifies labels into easy-to-digest information. Also provides alternative options if the product you scanned isn’t safe
Spokin (for iPhone); provides you with reviews on eating establishments, hotels, spas and food products from other food allergic people, as well as providing links to recipes and letting you follow other app users in your area

Other names for (white, black and brown) mustard include:

senf (German)
bach gioi tu, cai den (Vietnamese)
chieh, gai lat (Chinese)
iè mò (Mandarin)
gorchitsa belaya (Russian)
karashi (Japanese)
khardal (Arabic)
haradali (Swahili)
mostarda (Portuguese)
mostaza (Spanish)
moutarde (French)
rai, sarason (Hindi)
rayo (Nepali)
senape (Italian)
sinapi (Greek)

Mustard can be found lurking in a wide range of food products, including:

Savoury

Canned baby foods
Crisps and pretzels
Fritters
Fish sauce and paste
Hot dogs—mustard is a contaminant of hot-dogs, even without a mustard topping, because of the salesperson handling them—and hamburgers
Meals containing mustard greens
Pickles (onions and gherkins often contain mustard seeds in the vinegar) and piccalilli (a British mixed vegetable relish)
Pizzas
Potato salad
Processed and deli meats
Salad dressings, oils, and vinaigrettes
Sauces, including: barbecue, Béarnaise, chutneys, Cumberland, curry, gravies, honey mustard, Ketchup and tomato sauces, marinades, mayonnaises, dips, pesto
Seasonings and flavouring agents
Soups and stocks

Note on rapeseed or canola oil*: this oil is made from Brassica napus (rapeseed) and Brassica rapa (field mustard, turnip) seeds, which are in the same family as the seeds used to make mustard and could theoretically be problematic for the mustard-allergic. However, studies have shown that there is almost no protein left in the oil after processing—which includes seed cleaning, pressing, stripping, degumming and cooking in temperatures up to 107 °C (225°F)—and it does not cause allergic reactions.

As such highly refined rapeseed/canola oils are not considered dangerous for people with mustard allergy. But cold-pressed rapeseed/canola oil is less refined and can contain more residual protein. People with mustard allergy are therefore advised to avoid it.

* The term rapeseed oil is a generic term for oil made from Brassica species. The name “canola” is derived from ‘CANadian Oil, Low (erucic) Acid’. It was originally a trademark name of the Rapeseed Association of Canada but is now a generic term for all edible varieties of rapeseed oil in North America and Australasia.

Natural rapeseed oil contains high levels erucic acid, a monounsaturated omega-9 fatty acid which is produced in a wide variety of green plants, especially so in those of the genus Brassica. Edible rapeseed oil (aka canola oil, rapeseed 00 oil, LEAR (Low Erucic Acid Rapeseed) oil, and rapeseed canola-equivalent oil) is made from plants that were developed from cross breeding cultivars of B. napus and B. rapa and regulated to contain a maximum of 5% erucic acid in the EU and 2% in the US.

Sweet

Drinks

Several types of cocktail
Some craft beers like ‘French’s Mustard Beer’ and ‘ Torhouts Mustard Ale’

Non-food sources of mustard

Cosmetics

Rapeseed oil (Brassica napus) and cabbage extract (Brassica Oleracea) is used some skin products. Search for ‘ Brassica‘ in the ingredients list.

Alternative medicine

Rashes have been reported after the use of a mustard compress, mustard massage oil, and mustard-containing Chinese herbal medicine and pain-relieving liniment

Eating out

When it comes to restaurants and cafés in Europe, Article 44 of Regulation (EU) No 1169/2011 imposes a legal obligation on food businesses to provide information about the allergen content of non-pre-packaged foods. What this means is that, if the allergens are not listed on the menu or on other written material, the waiting staff must know what allergens are in the soup of the day so that they can tell you when you ask them about it.

All food sold in Australia and New Zealand must comply with food standards stated in Food Standards Australia New Zealand, Food Standards Code—Standard 1.2.3.

As in Europe, businesses must still display major allergen information next to foods that are not labelled (i.e. freshly prepared foods) or provide allergen information if requested by the customer. The code essentially recognises that both the customer and the restaurant have a responsibility to prevent an allergic reaction; the customer is responsible for telling staff of their allergy and, once notified, the restaurant staff are responsible for ensuring that food served to the customer does not contain the food(s) they are allergic to (i.e. by checking the ingredients, avoiding cross contamination during preparation and providing alternative options).

In Canada, some restaurants may provide ingredient and allergy information on their menus or online but they are not required to. It’s up to the customer to find out about ingredients and the possibility of cross-contamination by talking with restaurant staff.

n America, most states do not have food allergy regulations for restaurants. The exceptions are Illinois, Maryland, Massachusetts, Michigan, Rhode Island, Virginia, New York City and St. Paul, Minnesota. Restaurants in these states and cities are required to display food allergy awareness posters in the employee area and/or to place a notice on their menus (or menu boards, etc.) asking customers to inform the restaurant if anyone in their party has a food allergy and/or to have one person on the premises who is trained in food allergen safety. More details here.

Wherever you are, when you’re dining out, planning ahead is important. You can check the menus of restaurants on their websites and review them ahead of time. You can also call the restaurant and ask to speak to the manager about your food allergies, the restaurant’s menu items and their meal preparation practices.

Good communication is essential if you want to avoid bad situations. Remember to make it clear that you have an allergy rather than a food preference. Although the perils of peanut allergy are well-known in the catering sector, catering staff often do not appreciate that other food allergies can be just as dangerous. Always mention the potential seriousness of a reaction when ordering your food.

If you want to make sure that your allergy requirements are clear to everyone, you might want to consider carrying a chef’s card. This is essentially a note to whoever will be making your meal explaining what types of food you can’t eat and, depending on the card you choose, the precautions necessary to avoid cross-contamination. It can be given to your server or the manager so that they—and most importantly, the chef—are aware of your allergy.

You can make one yourself, download one for free, or buy one. There’s also, as ever, an app for that.

The Equal Eats app (for Android and iPhone) allows you to create personalised chef’s cards on the fly (the English version is free, other languages require a subscription) and the AllergySmartz app (for iPhone) allows you to translate your food allergies into different languages to ensure that precautions are taken during food preparation in restaurants.

You will find that most restaurants are very receptive to chef’s cards. It makes the whole dining-out-with-allergies experience easier and less stressful for everyone by ensuring that all the essential information is written down and everyone understands the severity of your allergy.

Some chef’s cards also address the issue of cross-contamination, which is when traces of an allergen are accidentally transferred to an allergen-free meal either directly during storage, or indirectly via, for example, an unwashed surface or utensil during cooking or serving.

In 2013 the US Food & Drug Administration (FDA) officially replaced the term ‘cross-contamination’ with ‘cross-contact’ to distinguish it from the contamination of food by pathogens like harmful bacteria. When you’re dining out in America and you discuss cross-contamination with a restaurant employee, they might recognise the word from their training, where it will have probably been used to describe foods being contaminated by biological pathogens. Some employees may be more familiar with the term cross-contact and may not realise that that’s what you mean when you mention cross-contamination. It’s your responsibility to explain that you’re talking about contamination with food allergens.

Beware of buffets and salad bars; many salads contain mustard and the serving utensils may be cross-contaminated. Similarly, the risk of contamination is high in fast food restaurants or food stalls where people handle multiple mustard-containing products.

Mustard is often used in European and Asian cuisines.

In Italian restaurants, look out for ‘mostarda,’ which is a chutney made from candied fruit, a touch of wine or vinegar and a mustard-flavoured syrup
In Spanish restaurants look out for ‘a la mostaza’, which is something in a mustard sauce
In Chinese restaurants look out for Kai Choi or Gai Choi or Jie Cai or Xuelihong (Chinese mustard greens)
Indian dishes often contain mustard seed and mustard oil

Other tips from the allergy literature include:

Beware bakeries; many items are made with some of the top allergens and there is a high risk of cross-contamination as goods are displayed unwrapped next to each other
Take-away food also has a high risk of cross-contamination because the serving spoons may have been used to ladle out different meals
Beware buffets if you have an allergy to a common food allergen, so that you can avoid cross-contamination on shared utensils
Beware restaurants that serve pre-made foods; these foods often do not come with ingredients lists, so the staff cannot be sure what’s in them and, as they are already put together, you can’t ask the chef to remove a trigger allergen from a meal that would otherwise by safe for you to eat
Stick to ‘simple’ menu items; sauces and gravies can contain hidden allergens that will not always be remembered by restaurant staff (and staff may not be aware of them if they come in pre-made foods)
Beware desserts, as they often contain at least some of the priority allergens and many restaurants get their desserts from speciality shops and may not know exactly what is in them
Eat out during off-peak times to ensure that staff have the time and mental bandwidth they need to be able to accommodate your needs; the first hour of the service period is probably the optimal time because staff are more likely to be alert and the kitchen is cleaner than it will be later on during the service period
Be sure to praise the staff after a good experience; they deserve it and they will remember you when you go back
Always take your medication with you!

Medications for mustard allergy

There are several types of medication available to help you deal with your mustard allergy, including:

antihistamines for mild symptoms ranging from rashes to hay fever-type irritations
eye drops and decongestants for watery eyes and blocked noses
fast-acting, powerful anti-inflammatory corticosteroids (derivatives of the natural steroid cortisol, aka glucocorticoids/systemic steroids) are used for the more severe symptoms of both IgE- and non-IgE-mediated diseases but, due to their side-effects, are not considered suitable for long-term use
corticosteroid creams for contact allergy
for people with non-IgE-mediated conditions like EoE and FPIES, swallowed topical corticosteroids can be used to reduce symptoms and (at least some) seem safe for long term use
inhalers for breathing problems; reliever inhalers to treat symptoms when they occur, preventer inhalers for everyday use to reduce the inflammation and sensitivity of your airways or combination inhalers for everyday use to help stop symptoms occurring and provide relief if they do
adrenaline/epinephrine auto-injectors for serious reactions

As with all allergies, these medications exist to help you deal with the symptoms of the allergy. They cannot cure you.

If you’ve had anaphylactic reactions in the past, you should have been prescribed an auto-injector. If you don’t have one, ask your doctor for a prescription.

It’s important to remember that antihistamines and corticosteroids can treat the milder symptoms of a food allergy, but in the case of a more severe reaction, there is no substitute for adrenaline—it’s the only medication available that can reverse the life-threatening symptoms of anaphylaxis. If you are having an anaphylactic attack, use your auto-injector.

As a rule of thumb, you should use your auto-injector if you experience severe symptoms—e.g. you can’t breathe properly, you’re going to pass out, you have severe hives—or a combination of symptoms from organ systems; for instance, if you develop a generalised rash (skin) and you start coughing repetitively (respiratory), or you start vomiting (gastrointestinal) and feeling faint (cardiovascular).

Other medications like anti-histamines should be given after the adrenaline has been administered.

If your symptoms can’t be controlled by the standard medications, the injectable drug omalizumab (a man-made antibody, brand name Xolair) may be able to help. It binds to IgE antibodies which, in turn, prevents them from binding with immune system cells, thus inhibiting the release of inflammatory mediators and reducing the symptoms of allergic reactions (or even stopping them from happening).

It’s only given in select cases to people whose allergies cause an undue burden, like:

people who suffer from severe and chronic reactions that don’t respond to medication, such as refractory anaphylaxis (a rare form of anaphylaxis with symptoms that persist even after adrenaline is administered) and serious occupational allergies
people who suffer from allergies that severely restrict their quality of life, like children with a history of severe reactions to multiple foods
people who are suffering side-effects from immunotherapy.

Omalizumab has an encouraging safety record, even when used for a long time, and has been credited with increasing the amount of trigger food(s) that someone can eat without experiencing symptoms, improving the results of immunotherapy and significantly improving a person’s quality of life (and, when applicable, that of their parents) thanks to reductions in dietary restrictions, reduced allergic reactions to accidental food exposure and a decreased risk of anaphylaxis.

Unfortunately, omalizumab does not seem to provide a permanent solution—when someone stops taking it, their allergic reactions return—so people with persistent food allergies have to keep taking it, and it’s not cheap. But if you have an uncontrollable food allergy and access to affordable medication, it’s definitely worth asking your doctor about.

A man’s hand holds a brightly lit light bulb against a black background.

Good to know

Working with mustard can be hazardous for your health.

Contact with mustard has been reported as causing skin rashes on the hands of:

Workers in factories producing fish sticks
People making salads
Farmers feeding cattle with mustard khal (cake), a high-protein supplement

People can also become sensitised to mustard and get allergic rhinitis—hay fever symptoms—from powdered mustard wafting through their working environment.

A risk factor for mustard allergy is atopy.

An atopic person is someone who is prone to developing an allergic reaction in response to a trigger. Studies have shown that the presence of other allergies is a risk factor for allergic reactions to food. Research has shown that this is no different when it comes to mustard allergy, and the presence of allergy to other foods is also a common factor.

Infants can become allergic to mustard without actually eating it.

Studies have shown that very young children can be sensitised to mustard. In a Finnish study, three children aged 12 to 18 months who had been breastfed for 11 months and had never eaten mustard had positive skin prick tests. In a French study, 8 children under the age of 3 (53% of those testing positive) showed symptoms after an oral challenge.

Because of these results, scientists have suggested that sensitisation in utero, during lactation and/or early consumption in baby foods may be happening, as it does with peanut and sesame seed.

Nasturtium flowers can cause reactions because of a compound they contain that is also found in mustard oil (isothiocyanate).

Isothiocyanate, produced by members of the Brassicaceae family as part of their defence against pathogen attacks, can cause nasty rashes on the hands of gardeners who touch the plants. It also makes Nasturtium flowers a delicious ingredient for salads and other dishes.

A yellow mustard-oil containing nasturtium flower