Advice for Dietitians

Anaphylaxis triggers

A wide range of foods can trigger anaphylaxis, but the most common culprits are peanuts, tree nuts (such as almonds, Brazils, hazelnuts and walnuts), sesame seeds, shellfish, fish, eggs and dairy products.

Avoiding peanuts and tree nuts

When buying pre-packaged foods, ingredient labels need to be checked thoroughly. Peanuts can appear under the names groundnuts, earth nuts and monkey nuts, and they may turn up among mixed nuts. Peanuts are actually legumes but elimination of other legumes (such as peas, beans and lentils) is not appropriate unless sensitivity is suspected.

Approximately 25 per cent of patients with peanut allergy react to tree nuts, such as almonds, walnuts, hazelnuts, Brazils or cashews. Doctors often advise that people who are allergic to one nut should avoid all others. There are a number of reasons for this: A person allergic to one nut may become allergic to others in due course; one nut may be sold as another (for example, almond desserts sold in restaurants may actually contain peanuts); and nuts may be stored together and therefore subject to cross-contamination.

Foods to watch out for include cakes, confectionery, biscuits, pastries, desserts, cereal bars, Satay sauce, vegetarian products, salad dressings, Indian, Chinese, Thai or Indonesian dishes.

Foods sold in restaurants and other catering outlets, or at bakery and delicatessen counters, are generally unlabelled and so pose a particular problem. Patients are advised to be direct with staff, pointing out the seriousness of their allergic condition. If staff cannot give an assurance that a specific dish is safe, it is best to eat elsewhere.

‘May contain’ labels are generally used where there is a known or suspected risk of contamination. Nut traces do sometimes occur, so it is best to avoid all foods carrying such a warning.

Allergic reactions to sesame

As with peanut, total avoidance is essential. Sesame is found in tahini, hummus and Chinese stir-fry meals are frequently cooked with sesame oil. Gomashio (a dry condiment often used in Japanese cuisine) is also made from sesame seeds.

Cross-contamination can be a problem with sesame, particularly in bakery products, and patients should be advised about this risk.

Allergic reactions to egg

The emulsifier known as lecithin can be derived from egg, although in practice this is uncommon. A patient who suffers severe reactions to egg should be advised to avoid egg lecithin but this is not necessary if the reactions are always mild. Manufacturers can be contacted to identify the source of the lecithin.

Some egg-allergic children can eat well-cooked egg (in cake, for example) without any ill effects, but not raw or lightly cooked egg. Others are allergic even to egg which has been well cooked. People who are fine with cooked egg are more likely to grow out of egg their allergy.

Allergic reactions to milk

As with egg allergy, allergic reactions to cow’s milk are usually mild but a few people do experience extreme reactions. People with milk allergy should avoid the following: whey, whey powder, whey solids, casein, caseinates and non-milk fat. Lactose is a milk sugar and in theory should not trigger allergic symptoms. But people with severe milk allergy have been known to react to lactose and this may be because residual traces of milk protein are present.