Oral allergy syndrome (OAS)

Symptoms

Children affected by oral allergy syndrome have immediate symptoms after eating food.

Common symptoms that occur are:

• redness, swelling or itching of the lips, inside of mouth and ears
• itching in the throat and ears

These symptoms are unlikely to progress but on occasion nausea, vomiting and hives can occur.

Understanding the reason

Although this is a food allergy, there is usually another cause. In most cases the primary allergy is to pollen (hay fever) or natural rubber (latex). You are allergic to the pollen or latex and because the allergen looks similar to proteins in some fruits, vegetables or nuts then you have an allergic reaction to the food. The scientific name for this is pollen-food syndrome or latex-food syndrome.

Different types of pollen can be responsible and in the UK, birch pollen (silver birch tree) is the most common. Grass pollens and weed pollens such as mugwort can also be responsible (see table).

Symptoms can be worse during the pollen season which for birch pollen is March to May.

Foods involved

Fresh fruit, raw vegetables and nuts are the most common cause of oral allergy syndrome (OAS). It may be that only very ripe fruit affects you or a certain colour of fruit. Some children can eat green apples but not red as an example. Certain features of the food may determine whether you have a reaction to it. Most times you will be able to tolerate the cooked or processed form of the food such as apple pie, juices, tinned fruit and sauces (see list below).

Managing oral allergy syndrome (OAS)

1. Avoid the food which causes the allergic symptoms in the raw state but the cooked or processed food may well be okay.
2. You don’t need to avoid all the foods in the ‘cross reactivity’ group unless the child has reacted to them.
3. Most children will only ever have a mild reaction to these foods (see symptoms).
4. Rinse your mouth out immediately and take an antihistamine as stated on your allergy plan.
5. Symptoms may be worse in the pollen season and a daily antihistamine may be appropriate.
6. Every child should have a management plan given to you at the allergy clinic.