Mustard allergy is a type of food allergy. Food allergy occurs when the body’s immune system wrongly identifies a food as a threat. When this happens, the body releases chemicals, such as histamine, in response. It is the release of these chemicals that causes symptoms.
It’s not known how many people in the UK have a mustard allergy, but it’s thought to be rare. But if you do have a mustard allergy, reactions can sometimes be serious.
Mustard is a type of plant that belongs to the Brassica family, which includes cabbage, Brussels sprouts and broccoli. There are various species of mustard plant.
Mustard plants have seeds that can be white, yellow, brown or black. The jars of mustard you see in supermarkets are made by grinding the seeds and mixing them with water, vinegar or other liquids. Different species are used to make different types of mustard.
Other parts of the mustard plant can be eaten or used in foods, including:
If you have a mustard allergy, these can all cause allergic reactions so it’s safest to avoid mustard in all its forms.
If you have hay fever caused by allergy to mugwort pollen (a weed that causes late summer hayfever), you may react to mustard and other foods in the Brassica family. This is known as Mugwort-mustard allergy syndrome. It happens because mugwort pollen contains a protein that’s similar to proteins in mustard. This type of mustard allergy is not common in the UK.
The symptoms of mustard allergy usually come on quickly, within minutes of eating the food.
Mild to moderate symptoms may include:
The term for this more serious reaction is anaphylaxis (pronounced ana-fil-ax-is).
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves difficulty breathing or affects the heart rhythm or blood pressure. Any one or more of the ABC symptoms above may be present.
In extreme cases there could be a dramatic fall in blood pressure. The person may become weak and floppy and may have a sense of something terrible happening. Any of the ABC symptoms may lead to collapse and lack of consciousness and, on rare occasions, can be fatal.
AIRWAY - swelling in the throat, tongue or upper airways, hoarse voice, difficulty swallowing
BREATHING - sudden onset wheezing, breathing difficulty, noisy breathing, persistent cough
CIRCULATION - dizziness, feeling faint, sudden sleepiness, confusion, pale clammy skin, loss of consciousness or collapse
If you think you may be allergic to mustard, see your GP who can refer you to a specialist allergy clinic if needed. They can find a clinic in your area from the British Society for Allergy and Clinical Immunology (BSACI).
It’s important to get a referral even if your symptoms were mild because it can be hard to tell if future allergic reactions could be more serious.
Once you get a referral, the consultant will discuss your medical history and symptoms with you. They might suggest skin prick tests, blood tests, and food challenge tests to help diagnose the allergy and work out how serious it may be.
Some clues that you might be at higher risk of more serious reactions are:
If you have asthma and it is not well controlled, this could make an allergic reaction worse. Make sure you discuss this with your GP or allergy specialist and take any prescribed medicines.
If you have mild allergic symptoms, you may be prescribed antihistamine medicine that you take by mouth. But if you are at risk of a serious allergic reaction (anaphylaxis), you may be prescribed adrenaline – the emergency medicine used to treat anaphylaxis. It is also known as epinephrine.
Because anaphylaxis can happen very quickly, adrenaline is available in different forms that are designed to be easy to use. It’s important to know exactly how and when to use your prescribed adrenaline. Healthcare professionals can show you how to use it, and there are also resources such as practice devices and videos on manufacturer websites.
Options currently available on prescription in the UK include:
You must carry two in-date forms of prescribed adrenaline at all times as a second dose may be needed if symptoms do not improve after five minutes or get worse.
Once you have been diagnosed with a mustard allergy, you will need to avoid mustard and foods that contain it.
Read the ingredient lists on food packets carefully every time you shop. Mustard is included in the list of top 14 major food allergens in the UK. This means it must be highlighted on ingredients labels, in bold for example.
Read the ingredient list every time you buy a product as manufacturers change their recipes often.
When eating out
Restaurants, cafes, hotels, takeaways and other catering businesses are required by law to provide information on major allergens, including mustard. Ask staff directly if the food you’d like to buy contains mustard and if there is a risk of cross-contamination and let them know that even small quantities can cause a reaction. Don’t be afraid to ask staff to check with the chef.
Mustard can be used in a wide range of foods, for example:
Provide your email address to receive our printable guide outlining emergency symptoms and actions.
Additionally, enjoy our monthly Allergy Outlook email, delivering the latest news, updates, and resources directly to your inbox.
