Treatment of food allergies

The treatment or management of IgE-mediated food allergies can be approached in two different ways. First, allergic reactions can be treated pharmacologically to resolve the symptoms. But, second and preferably, the avoidance of the allergenic food(s) will prevent the occurrence of allergic reactions.

Pharmacological approaches

AAAAI

American Academy of Allergy, Asthma and Immunology

The pharmacological treatment of allergic reactions is also primarily a clinical situation. Again, we will direct you to medical web sites (see box at right) that can provide expert advice on this subject. Obviously, this aspect should be addressed with a physician or allergist.

Pharmacological approaches are available for the treatment of the symptoms that occur during an allergic reaction. Anti-histamines are useful drugs for treatment of most mild to moderate allergic reactions and function by blocking histamine receptors in the tissues. Epinephrine or adrenaline is a much more powerful drug that has the ability to resolve severe anaphylactic reactions in many cases. Those patients with a history of life-threatening reactions to foods are typically advised to carry an epinephrine-filled syringe with them at all times.

Avoidance diets

The major approach to the treatment for true food allergies is their prevention their occurrence through implementation of a specific avoidance diet. For example, a peanut-allergic person would be advised to avoid peanuts in all forms. Considerable responsibility is placed upon these individuals; they must acquire considerable knowledge of food composition. Dietitians can be helpful in teaching clients to interpret food labels to detect ingredients made from the offending food. Compliance with such avoidance diets is enhanced if the number of foods eliminated is kept to a minimum. Thus, accurate diagnosis is an important initial step.

Only a few hypoallergenic foods are available for use by food-allergic individuals. In the case of infants with cows' milk allergy, several alternative formulae can be fed. Soybean-based infant formula works well in many cases, although some infants will develop soybean allergy as a result of that exposure. Casein hydrolysate formula can also be used successfully in the majority of cases. This formula is based upon extensively hydrolyzed casein. Although casein is a common cows' milk allergen, the hydrolysis of the casein to a mixture of very small peptides and amino acids eliminates the allergenicity for the vast majority of milk-allergic infants. However, a few exceptional case reports of allergic reactions to casein hydrolysates. In such extreme cases, an elemental formula can be used; these formulas are based upon synthetic amino acids and other simple chemical and nutritional components.

Cross-reacting foods

In the construction of safe and effective avoidance diets, questions also often arise regarding the potential allergenicity of closely related foods. Cross-reactions occur between closely related foods in the case of certain food groups but not others, so it does not seem to be possible to offer uniform advice for all related food groups. But, cross-reactions are quite common with certain food groups including the various crustacean species (shrimp, crab, lobster, and crawfish), different species of avian eggs, and milk from various mammalian sources (cow, goat, sheep, etc.). However, for other food groups, advice regarding the likelihood of cross-reactions between related foods is not so clear. For example, individuals with allergies to one or more species of fish can sometimes consume other fish species without adverse reactions. Still, most fish-allergic individuals are advised to avoid all species of fish and that appears to be rather prudent advice for many of them. The patterns of fish allergy appear to be variable from one individual to another.

Also, a few peanut-allergic individuals are allergic to other legumes such as soybeans, but this is definitely not a common occurrence. Clinical hypersensitivity to one legume, such as peanuts or soybeans, does not warrant exclusion of the entire legume family from the diet unless allergy to each individual legume is confirmed by clinically.

Possible cross-reactions among tree nuts or between peanuts and tree nuts are another difficult topic. Peanuts, as just mentioned, are legumes and are not closely related to any of the tree nuts. The most commonly allergenic tree nuts (e.g. walnut, almond, hazelnut, cashew, etc.) are for the most part not closely related to one another either. A few are botanical cousins including walnut and pecan and cashew and pistachio. Most tree nut-allergic individuals are advised to avoid all tree nuts and some clinical evidence of cross-reactivity does exist. Many tree nut-allergic individuals also report allergy to peanut although it is unclear if this is the result of cross-reaction or separate forms of allergic sensitization.

Allergens are proteins and related proteins can indeed occur in divergent genetic sources. The well described cross-reactivity of birch pollen and apple is an outstanding example. In many cases, more intense biochemical investigation is needed to sort out the cross-reactivity that may exist among divergent (or in some cases closely related) species to provide optimal advice about avoidance diets.

In addition to cross-reactions among related foods, cross-reactions are also known to occur between certain types of pollens and foods especially with OAS. Examples would include ragweed pollen and melons, mugwort pollen and celery, mugwort pollen and hazelnut, and birch pollen and various foods including carrots, apples, hazelnuts, and potatoes. However, only a sub-set of pollen-allergic individuals experience OAS with certain foods.

Cross-reactions are also known to occur between allergies to natural rubber latex and certain foods such as banana, chestnut, and avocado. Latex allergy is primarily a skin contact allergy associated with exposure to allergens in gloves made from natural rubber latex (or to other latex materials). Cross-reactions to various foods among individuals with latex allergy is not common.