Avoiding nuts in food

Exposure to peanuts or tree nuts can occur through ingestion, touch or inhalation of the allergen and trace amounts can trigger a reaction. Management of the problem involves strict avoidance and self-treatment to deal with inadvertent exposures.

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. Heating may reduce the allergenicity of heat-labile allergens (e.g. fruit, hen’s egg and cow’s milk) but increases the allergenicity of nuts).

Food to watch out for include cakes, confectionery, biscuits, pastries, ice cream, desserts, cereal bars, Satay sauce (which is made with peanuts), vegetarian products, curries, salad dressings, pesto sauce (which is made with nuts), 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.

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Should peanut oil be avoided?

Research into the allergenicity of peanut oil has taken place in Southampton and was published in the British Medical Journal in April 1997. The researchers conclude that refined peanut oil will not cause allergic reactions for the overwhelming majority of acute peanut allergic individuals, and if anyone does suffer a reaction it is likely to be mild. The Anaphylaxis Campaign has full details of the Southampton project, available on request.

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What about other nuts or legumes?

Peanuts (Arachis hypogaea) are actually legumes but elimination of other legumes (such as peas, beans and lentils) is not appropriate unless sensitivity is suspected. Bernhisel-Broadbent, J & Sampson, H.A. (1989) [J Allergy Clin Immunol 83: 435-40] found that only five per cent of their selected population of legume reactive children had symptoms with multiple legumes.

Approximately 25 per cent of patients with peanut allergy react to tree nuts, such as almonds, walnuts, hazelnuts, Brazils or cashews. However, some peanut allergic patients find they can eat tree nuts without a problem. Individuals who are uncertain should seek referral to an NHS allergy clinic where a detailed diagnosis can be made.

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.

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Allergic reactions to sesame

Although peanuts have dominated the headlines, a small but significant number of people experience severe allergic reactions to sesame seeds. As with peanut, total avoidance is essential. It is likely that heating does not destroy the allergenicity of sesame, and sesame oil is likely to be unrefined and therefore unsafe. Dishes containing sesame include tahini, gomashio and hummus, and Chinese stir-fry meals are frequently cooked with sesame oil. Sometimes sesame is to be found in Aqua Libra.

Cross-contamination can be a problem with sesame, particularly in bakery products, and patients should be advised about this risk. For example, sesame seeds were found embedded in teacakes sold in a major supermarket. There was no mention of them on the label.

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Allergic reactions to egg

Egg allergy is usually mild, but in rare cases can trigger anaphylaxis. Food labels must be thoroughly scrutinised for products containing egg or albumen. 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.

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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.

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