What is a food allergy?

A vegetable 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 the allergic symptoms.

There are different types of vegetable allergy. Symptoms could be due to:

 

Sometimes symptoms can be more serious and you may be at risk of anaphylaxis.

You can also read about allergies to fruit

Download our allergy to vegetables factsheet

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Varieties of vegetables that trigger allergies

Any vegetable has the potential to cause an allergic reaction. The following are some of the vegetables that are commonly eaten in the UK that can cause reactions, but it is not a complete list.

  • Aubergine
  • beetroot
  • cabbage
  • carrot
  • celery
  • cucumber
  • garlic
  • lettuce
  • mushroom
  • onion
  • peppers
  • sweetcorn
  • potato (sometimes potato starch is used as an anti-caking agent in a pizza).

Pollen food syndrome

Pollen food syndrome usually occurs in people with hay fever who are allergic to pollens. It can cause allergic reactions when you eat certain vegetables or fruits. This is because the proteins in pollen are similar to the proteins in the vegetables and fruits.

Symptoms are usually mild and may respond to antihistamines, but speak to your doctor to make sure this is the right treatment for you.

Symptoms of pollen food syndrome usually include:

  • redness, mild swelling or itching of the lips, tongue, inside of the mouth, soft palate and ears
  • itching and mild swelling of the throat.
  • occasionally, people might also have symptoms in the oesophagus (food pipe) or stomach, causing abdominal pain, nausea and vomiting
  • sneezing, runny nose, or symptoms affecting the eyes.

 

Rarely, more serious symptoms can occur, known as anaphylaxis (anna-fill-axis).

Serious symptoms are unusual because the proteins that cause the allergy are unstable and are destroyed with heat or once they reach the stomach. Most people with pollen food syndrome have allergic reactions if they eat the raw vegetables, but they are able to eat the cooked vegetables without any problem.

More serious allergy symptoms

Most people with an allergy to vegetables have pollen food syndrome, but some people have more serious reactions which are not related to pollen.

More serious symptoms are often referred to as the ABC symptoms and can include:

  • AIRWAY – swelling in the throat, tongue or upper airways (tightening of the throat, hoarse voice, difficulty swallowing).
  • BREATHING – sudden onset wheezing, breathing difficulty, noisy breathing.
  • CIRCULATION – dizziness, feeling faint, sudden sleepiness, tiredness, confusion, pale clammy skin, loss of consciousness.

 

The term for this more serious reaction is anaphylaxis (anna-fill-axis).

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 unconsciousness and, on rare occasions, can be fatal.

Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves the ABC symptoms.

These serious symptoms may be accompanied by:

  • nettle rash (known as hives or urticaria) anywhere on the body
  • a tingling or itchy feeling in the mouth
  • swelling of lips, face or eyes
  • stomach pain or vomiting.
Read more about anaphylaxis

Allergy to lipid-transfer proteins (LTPs)

Lipid-transfer proteins (LTPs) are proteins found in plants. Lipid Transfer Protein Syndrome is an allergy affecting people who have become sensitised to LTPs. It can cause reactions to vegetables, fruits, nuts and/or cereals, and reactions can be serious.

Food intolerance

Some people who have symptoms when they eat a food have a food intolerance rather than an allergy. A food allergy is a reaction of the immune system, whereas food intolerance may have a different cause.

Intolerance to vegetables could be part of a wider intolerance to foods caused by a sensitivity to chemicals that are present naturally in the vegetables, or an inability to digest the sugars found in them.

A food intolerance can have a much wider range of symptoms, including:

  • migraine
  • fatigue
  • tummy (abdominal) pain
  • bloating and frequent diarrhoea
  • muscle and joint pains
  • blocked or runny nose.

Sensitivity to chemicals

Another possibility is that you are sensitive to chemicals that exist naturally in many foods. This can cause symptoms, but is not the same as an allergy.

For example, salicylates are found in the skins of some vegetables and fruits, as well as tea, spices, honey, ginger and some drinks. They are also found in aspirin. Salicylates can cause wheezing or other symptoms such as nettle rash (hives).

Vaso-active amines are also found in some fruits, vegetables and other foods. In sensitive people, they can cause headaches, rashes, flushing, itching, swelling, runny or blocked nose, irregular heartbeat, diarrhoea, nausea, vomiting or abdominal pain.

Getting a diagnosis

If you think you may be allergic to vegetables, 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 or intolerance and work out how serious it may be.

Some clues that you might be at higher risk are:

  • you have already had a serious reaction, with any of the ‘ABC’ symptoms
  • you have asthma, especially if it is not well controlled
  • you have reacted to a tiny amount of the food.

 

If the symptoms only affect your mouth, the likelihood is that your allergy will remain mild, but you must still seek medical advice.

Read about allergy testing

Treating symptoms

If you have mild allergic symptoms you may be prescribed antihistamine medicine that you take by mouth. If you are at risk of anaphylaxis, you may be prescribed adrenaline to use in an emergency.

Adrenaline comes in pre-loaded adrenaline auto-injectors (AAIs) that are designed to be easy to use. Make sure you know how and when to use them. Ask your healthcare professional to show you, and find help on the manufacturer’s website.

The adrenaline auto-injectors prescribed in the UK are:

 

You must carry two with you at all times, as you may need to use a second one five minutes after the first if your symptoms don’t improve or get worse.

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.

Read more about what to do in an emergency

Key messages

  • If you have symptoms after eating vegetables, visit your GP.
  • If you are prescribed adrenaline auto-injectors, carry them with you at all times.
  • Always be guided by your allergy specialist on which foods to avoid.
  • If you have asthma, make sure it is well managed. See your GP about this.

Download our allergy to vegetables factsheet

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