What is Cross-Reactivity and Pollen Food Allergy Syndrome?

Do you suffer from hay fever? Have you ever noticed that you also have a food allergy?

This sensitivity is called cross-reactivity. It occurs when the body’s immune system treats the proteins in pollen as being similar to the proteins in a fruit or vegetable and this can result in a food allergy.

How the body reacts to pollen  

If you are allergic to pollen your body will react as if it is a dangerous substance. Chemicals are released to fight the pollen intrusion including immunoglobulin E (IgE) antibodies which then trigger the release of histamines. 

Food allergy and cross-reactivity

Some foods contain the same type of protein as pollen. It means that the body reacts in the same way as it does to pollen. So, if you eat tomatoes, you might have an allergic reaction.

The role of histamines

It is the chemical histamine that causes the symptoms you recognise as an allergic reaction. For example, the most common symptoms of hay fever (allergic rhinitis) are:

• A blocked-up or runny nose
• Sneezing
• Itchy, red, and watery eyes
• A sore throat or cough
• Allergic asthma
• Fatigue

Foods that might also cause an allergic reaction

If you have a pollen allergy, the type of pollen you are allergic to will determine which foods cause Pollen Food Allergy Syndrome (PFAS) or Oral Allergy Syndrome (OAS). 

Have a look at this chart to find the pollen that gives you your allergy together with some of the foodstuffs you may need to avoid because there is a cross-reactivity between these foods and pollen. 

These foods contain similar proteins to grass, tree and weed pollen. However, your intolerance might only appear during the hay fever season and not all year round. Symptoms could include swollen lips, itching around the mouth and lips or an itchy throat. 

For most people, symptoms of food cross-reactivity aren’t serious and will disappear within an hour or so of eating the food. Severe reactions might mean you have an actual allergy to a certain food, rather than a reaction caused by cross-reactivity. 

Managing your allergy

Most people find that their allergy comes from eating raw or lightly cooked food. Cooking gets rid of the allergens so you may find you can eat foods affected by cross-reactivity as long as they are cooked. 

A good example of this is when you eat an apple. Eaten raw the apple may provoke an allergic reaction. But if you eat apples that have been cooked to make a crumble or pie you might not experience any sort of reaction.

If you can’t eat certain foods cooked or raw, then it is best to avoid eating them altogether.

Testing for a food intolerance or an allergy

A simple finger-prick blood test can confirm a food allergy. There are normally two types of test. An IgE test will confirm if you have a food allergy. An IgG test will confirm food sensitivity or intolerance. 

Taking a test will help you to manage your symptoms as you’ll know what foods to limit or avoid. If you have a food allergy, then it’s important to see a medical professional to find out more about your condition and how to treat it.