Oral allergy syndrome (OAS) is a cross-reaction caused by the body mistaking a food allergen for an allergen it is already allergic to such as pollen. People most likely to get OAS usually have hay fever in the spring and/or summer, caused by tree and/or grass pollen.
Which foods are involved?
Some foods are more commonly associated with pollens than others. Apple, strawberry, kiwi, stone fruits and tree nuts are the commonest foods to cause OAS in the UK. If you are allergic to pollen, many of these foods will show up as a positive test on skin prick testing, because of the cross-reactions. Don’t cut out all foods which are positive, only those you have a reaction to. If you think you have OAS to a particular fruit or vegetable try the same food cooked or canned.
What are the symptoms?
Typical symptoms include immediate itching and sometimes swelling of the lips, tongue, mouth and soft palate (roof of the mouth). These symptoms usually occur when eating certain raw fruits, vegetables or nuts. Some people only react to one food; others react to many different foods. If your symptoms are to raw nuts, you may still react to cooked nuts but it is worth testing as some people can eat cooked nuts. Even if you only react to one nut, you may need to avoid all nuts due to cross-contamination. Most reactions are not life-threatening although sometimes reactions to nuts can be severe. If you are asthmatic you should have a skin prick test before you test.
Medications
Antihistamines are helpful in relieving the symptoms of oral allergy syndrome. If reactions are severe, you may have been prescribed an Epipen, which you must always carry with you. If you have asthma, make sure it is well controlled and use your inhaler if foods make you wheezy.
Appointments are available in my food allergy clinic for advice and dietary management.