My recent interest in learning more about allergies and related conditions has led me to some favourite topics. In my top three is cross-reactivity of allergens, it interests me as most mainstream media talk about allergy in the singular, but from experience as parents we find that our children rarely have a single allergy.
My daughter is lucky, she is only allergic to two types of food, but also seems to suffer from hayfever from February to September, so must also be allergic to a range of pollens and possibly moulds. I aim to come up with a more definitive list by signing up to Pollen Diary, take a look at their website here. It is free to use, you record symptoms daily and it can give you analysis on which pollens you are likely to be allergic to… anyway, I digress.
There is a condition called Oral Allergy Syndrome (OAS), sometimes also known as Pollen Food Syndrome which mostly affects people who already suffer from hayfever (pollen allergies/seasonal rhinitis) and this is due to cross reactivity.
The symptoms of OAS are similar to those of food allergies, swelling and/or itching of the mouth, lips, tongue and/or face after eating raw fruit, vegetables, nuts and/or spices.
It very rarely leads to anaphylaxis and it is less often associated with the other symptoms of food allergies, such as wheezing, hives, vomiting or digestive problems.
The symptoms are usually more short-lived than the symptoms of food allergy and ease quickly with anti-histamines.
The cause of OAS are proteins in certain fruit and vegetables that are cross reactive with pollen. For example birch with peach, apple and cherry. The body recognises the proteins in the fruit/vegetable are similar in structure to those of the pollen you are already sensitive to, so there is a contact allergic reaction.
Onset of OAS
Age of onset for Oral Allergy Syndrome seems to be in adulthood, with people having to experience hayfever symptoms before experiencing OAS. There has been an increase in the number of children with OAS as children have started to experience hayfever at an increasingly young age.
Which foods cause symptoms?
We recently ran a survey on OAS with CAN Research Group and the results were quite interesting for such a small group of respondents.
We were initially looking for a link between pesticide use and OAS, but we were unable to find enough respondents who ate all organic fruit and vegetables.
The top offending groups were tropical fruit (banana, kiwi, mango etc.), apples, pears and stoned fruit (cherries, peaches etc.). The least problematic food for OAS sufferers were beetroot and brassicas. See the references below for tables showing which pollens are linked to which food.
If you think that you or your child are affected by Oral Allergy Syndrome you should keep a food diary and make an appointment to see your GP. They should be able to diagnose you on symptoms alone.
A skin prick test may be undertaken by some health professionals, but the results with fruit and vegetables are not currently standardised.
There is currently no treatment for Oral Allergy Syndrome, there are occasionally studies undertaken to reduce the effects using Immunotherapy, but this is not currently an option on the NHS. Options are:
- Antihistamines can be taken to alleviate symptoms
- Avoidance of foods causing symptoms
- Cooking/heating/freezing offending food (note is unlikely to work with nuts)
- Eating fresh or partially unripe fruit
- Peeling fruit/vegetables
- Eating the food outside of pollen season may give reduced symptoms
There are many anecdotal tales of pesticides on fruit and vegetables triggering the onset of OAS, but there is currently no evidence to support this theory. You can supposedly eat organic or homegrown pesticide free variety of the food which causes symptoms and this can allow you to eat more before experiencing symptoms. This is more likely due to organic fruit being more fresh and fresher fruit is thought to cause less symptoms.