Food Allergies

FOOD ALLERGIES

An allergy is an altered reaction of the tissues of some individuals to substances that, in similar amounts, are harmless to other people. The substances causing hypersensitivity are called allergens. Some common allergens are pollen, dust,animal dander (bits of dried skin), drugs, cosmetics, and certain foods. This discus-sion will be limited to allergic reactions to foods. A food allergy occurs when the immune system reacts to a food substance, usually a protein. When such a reac-tion occurs, antibodies form and cause allergic symptoms. An altered reaction toa specific food that does not involve the immune system is called (the specific food) intolerance. Approximately 2% to 8% of children and 2% of adults are known tohave food allergies; many of these allergies began in the first year of life.

Types of Allergic Reactions

Sometimes allergic reactions are immediate, and sometimes several hours elapse before signs occur. Allergic individuals seem most prone to allergic reactions during periods of stress. Typical signs of food allergies include hay fever, urticaria, edema, headache, dermatitis, nausea, dizziness, and asthma (which causes breathing difficulties).

Allergic reactions are uncomfortable and can be detrimental to health.

When breathing difficulties are severe, they are life-threatening.

Allergic reactions to the same food can differ in two individuals. For example, the fact that someone gets hives from eating strawberries does not mean that an allergic reaction to strawberries will appear as hives in another member of the same family. Allergic reactions can even differ from time to time with the same individual.

Treatment of Allergies

The simplest treatment for allergies is to remove the item that causes the aller-gic reaction. However, because of the variety of allergic reactions, finding the allergen can be difficult.

When food allergies are suspected, it is wise for the patient to keep a food diary for several days and to record all food and drink ingested as well as allergic reactions and the time of their onset. Such records can help pinpoint specific allergens. Some common food allergens are listed in Table 10-4. It is common for other foods in the same class as the allergens to cause allergic reactions as well. Cooking sometimes alters the foods and can eliminate allergic reactions in some people.

Laboratory tests may be used to find the allergen or allergens. The RAST (radio allergosorbent test), for example, may be used to determine which com-pounds are causing allergic reactions. Skin tests are sometimes used to detect allergies. However, food allergies can be difficult to determine from skin tests.

After completion of the allergy testing, the client is usually placed on an elimination diet. For 1 or 2 weeks the client does not eat any of the testedcompounds that gave a positive reaction. The client includes in the diet the foods that almost no one reacts to, such as rice, fresh meats and poultry, noncitrus fruits, and vegetables. Sometimes, these diets allow only a limited number of foods and can be nutritionally inadequate. If that is the case, vitamin and mineral supplements may be prescribed.

When relief is found from the allergic symptoms, the client is continued on the diet, and, gradually, other foods are added to the diet at a rate of only one every 4 to 7 days. Those foods most likely to produce allergic reactions are added last until an allergic reaction occurs. The allergy can then be pinpointed, and the offending foods eliminated from the diet. Knowing the cause of the al-lergy enables the client to lead a healthy, normal life, provided that eliminating these foods does not affect her or his nutrition.

If the elimination of the allergen results in a diet deficient in certain nutrients, suitable substitutes for those nutrients must be found. For example, if a client is allergic to citrus fruits, other foods rich in vitamin C to which the client is not allergic must be found. If the allergy is to milk, soybean milk may be substituted.

The client must be taught the food sources of the nutrient or nutrients lacking so that other foods can be substituted that are nutritionally equal to those causing the allergy. It is essential that the client be taught to read the la-bels on commercially prepared foods and to check the ingredients of restaurant foods carefully. Baked products, mixes, meat loaf, or pancakes may contain egg, milk, or wheat that may be responsible for the allergic reaction.

Sometimes, however, the allergies require such a restriction of foods that the diet does become nutritionally inadequate. As in all cases of allergy, and particularly in such cases, it is hoped that the client can become desensitized to the allergens so that a nutritionally balanced diet can be restored. The client is desensitized by eating a minute amount of food allergen after a period of com-plete abstinence from it. The amount of the allergen is gradually increased until the client can tolerate it.