Mustard Allergy
Mustard allergy is relatively rare in the UK, but for those affected it can sometimes cause serious reactions. If you think you or your child may be allergic to mustard, speak to your GP for advice and possible referral to an allergy clinic.
Overview
Mustard allergy happens when the body’s immune system identifies mustard proteins as harmful, releasing chemicals such as histamine that cause allergic symptoms. Even though not many people in the UK are affected, reactions can be significant.
Mustard basics
Mustard belongs to the Brassica family (alongside cabbage, Brussels sprouts and broccoli). The seeds may be white, yellow, brown or black. When ground and mixed with water, vinegar or other liquids, they make the jars of mustard found in shops. However, other parts of the mustard plant are also used in food:
- Mustard leaves
- Seeds and sprouted seeds
- Flowers
- Mustard oil
- Mustard cress
If you have a mustard allergy, you may react to any form of the plant, so complete avoidance is safest.
Mugwort–mustard allergy syndrome
Some people with hay fever caused by mugwort pollen may also react to mustard and other Brassica foods. This is called mugwort–mustard allergy syndrome and is due to proteins in mugwort pollen being similar to those in mustard. It is not very common in the UK but worth knowing about if you have hay fever and react to mustard.
Symptoms
Mild to moderate symptoms may include:
- Hives (itchy raised rash)
- Itching or tingling in the mouth
- Swelling of lips, face or eyes
- Stomach pain or vomiting
Severe symptoms (anaphylaxis) can include:
- Airway: swelling in throat or tongue, difficulty swallowing, hoarse voice
- Breathing: wheezing, shortness of breath, noisy breathing
- Circulation: dizziness, faintness, confusion, pale clammy skin, collapse
Who is at higher risk?
- Previous serious reaction with ABC symptoms
- Asthma, especially if not well controlled
- Reactions to very small amounts of mustard
Treatment
Mild reactions may be treated with antihistamines. If you are at risk of anaphylaxis, you should carry two prescribed adrenaline auto‑injectors (such as EpiPen® or Jext®) at all times. Learn how to use them, and always call 999 if adrenaline is used.
Avoiding mustard
Mustard is one of the 14 major allergens in the UK, so it must be highlighted on food labels. Still, always check labels carefully, as recipes and ingredients may change. Eating out is higher risk due to hidden mustard in sauces, marinades or spice mixes. Make staff aware of your allergy every time you eat out.
Foods that may contain mustard
Mustard can appear in many foods, including:
- Mayonnaise and barbecue sauce
- Ketchup and tomato sauces
- Fish paste
- Processed meats and sausages
- Pickles, piccalilli and marinades
- Pizza toppings
- Salad dressings and oils
Mustard seeds and oil are common in cuisines such as Indian, Russian and Mediterranean. In Italian cooking, watch for “mostarda” — a mustard syrup with fruits served alongside meats. The proteins in mustard are heat stable, so reactions can occur even after cooking.
What else to look out for
Cross‑reactivity may happen with seeds of other Brassica family plants. If you think you react to other seeds, mention it to your allergy specialist.
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Important to know
- Always speak to your GP if you think you may have a mustard allergy.
- Carry prescribed AAIs and know how to use them.
- Check labels every time you shop.
- Inform restaurants and caterers about your allergy.
- Keep asthma well controlled.