Updated 24 May 2017

Peanut allergy update

An allergy to peanuts is probably the most serious type of food allergy known to man, as it is often fatal. To make matters worse, minute quantities can trigger a reaction.

A paper published this year by Du Plessis and Steinman* in Current Allergy and Clinical Immunology, the journal of the Allergy Society of South Africa, has provided a number of interesting new insights.

Why is the incidence increasing?

The incidences of peanut allergies are on the increase. This is probably due to a combination of the following factors:

1. The general increase in allergic or atopic reactions in the population. Humanity is becoming more allergic to an ever-increasing number of allergens. The reasons for this are not clear, but two possible contributing factors are: the increase in potential allergens in modern life because of the endless array of processed foods and drinks that are constantly being added to our menu, and the fact that if two individuals who are allergic to certain products marry, their children will inherit ‘allergy genes’ from both parents, thus increasing their potential to react to even more foods and other products.

2. The tendency of food manufacturers to use peanuts in a wider range of products. This is also a feature of modern life. People in the 21st century demand variety and new products all the time, and food manufacturers respond by creating foods that are more and more varied. In the past, the average person would probably only have been exposed to peanuts as a staple food or snack eaten on its own, whereas nowadays peanuts are found in breakfast cereals, chocolate and confectionery, baked products, ice creams and many other foods. Because of the rising cost of other nuts (Brazil, walnut, macadamia, pecan etc.) food manufacturers turn to peanuts as a less expensive alternative in recipes that call for the use of nuts.

3. The globalisation of our food supply. Twenty years ago restaurants serving exotic foods were few and far between, but today, we who live in the global village can pop into a restaurant at our local mall and eat typical Thai, Indian, Chinese and other cuisines. Many of these exotic dishes contain peanuts in some form or other. Peanut oil, for example, is a popular ingredient in oriental cooking.

4. An increase in the consumption of peanuts and ‘hidden’ forms of peanuts. You may eat a peanut without even being aware of the fact, or peanut-free foods may be contaminated with minute traces of peanut if the foods you buy have been manufactured in a factory that also processes peanut-containing foods. This is the reason why most food manufacturers display a warning on their products stating “May contain traces of peanuts” to cover themselves against litigation in case someone suffering from a severe peanut allergy should eat one of their peanut-free foods and develop allergic reactions to the tiny quantity of peanut contaminant in that food.

5. The use of products derived from peanuts in non-food products, i.e. peanut oil that is used extensively in cosmetics (soaps, skin creams etc.).

6. Transfer of peanuts to infants via breast milk. Most people develop peanut allergies as a result of being exposed to peanuts over a long period, but some children will present with a full-blown allergic reaction the first time they eat peanuts. Some researchers believe this is due to that fact that these children were sensitised by tiny quantities of peanut while being breast-fed.

What other plant foods are related to peanuts?
Contrary to their name, peanuts are not actually nuts, but belong to the legume family. Peanuts are, therefore, not botanically related to nuts that grow on trees (e.g. walnuts, pecan nuts etc.).

Approximately 15% of individuals with peanut allergies may also react to other legumes, such as dry beans, peas, and lentils, soy beans and all products made from soy, for example tofu and textured vegetable protein, which is added to nearly all processed foods. Lentils in particular may cause allergic reactions in individuals with peanut allergies.

Unfortunately, 25-35% of people who are allergic to peanuts may also develop allergic reactions to tree nuts, despite the fact that these foods are not botanically related.

What is the effect of heat treatment?
Studies have shown that roasted peanuts are more inclined to cause allergies than raw peanuts.

The Chinese practice of frying or boiling peanuts causes a less pronounced increase in the allergic potential of the proteins in peanuts that cause the allergic reaction. Dry roasting, which uses much higher temperatures has a negative effect on the allergenicity of peanuts, thus increasing their allergic potential considerably.

This difference in the effect exerted by cooking methods may be one reason why peanut allergy appears to be more prevalent in western countries.

The lowdown on peanut oil
The oil that is extracted from peanuts can either be non-allergenic (acid-extracted, heat-distilled, high-processed oils) or allergenic (cold-pressed or extruded oils), which will cause allergic reactions in approximately 10% of people who are allergic to peanuts.

Unfortunately, it is practically impossible to find out if the peanut oil used in the preparation of restaurant or processed food is high-quality, heat-extracted or low-quality, cold-pressed oil. Therefore, it is better to avoid all contact with peanut oil if possible. – (Dr I.V. van Heerden, DietDoc)

Any questions? Ask DietDoc


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Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies.

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