Food allergy

The body has immune functions^(*1)to protect from being damaged by bacteria, viruses, etc. Allergy is responses (hypersensitivity) to substances, such as egg, cedar pollen and mites, which do not directly damage the body but causes symptoms, such as asthma and atopic dermatitis.

Food allergy is caused by protein in diet, which is absorbed in the digestive tract unlike mites or cedar pollen taken percutaneously or through the respiratory tract.

The diagnosis of food allergy is confirmed by provocation test^(*2)to investigate whether or not ingesting a suspected food causes symptoms, taking blood test into account. The diagnosis procedure is not used uniformly so that changes in the number of patients with food allergy have not been investigated systematically or longitudinally.

In general, however, the number of allergic diseases has been increasing and a crop of new foods has been created with the progress of the distribution system. It is thus highly likely that the number of patients with food allergy has been increasing. A questionnaire survey showed that 9.3% of the adults had food allergy, suggesting that food allergy is more than children's problem.

Food allergy reflects one's eating habit. For example, peanut allergy is common in the United States. In Japan, eggs, milk and soybean used to be the three major allergens (allergy-causing substances). With the changes in eating habits, more and more seafood protein has been being consumed instead of soybean protein and thus become a major food allergen.

One treatment for food allergy is elimination diet therapy by avoiding causal foods. When causal foods are principal foodstuffs -- this is often the case -- they must be eliminated from daily diet during the therapy. In that case, alternative diet with substitute foods is required for nutritional supplementation. Physicians are in charge of counseling but close communication with dietitians is important and dietitians' active involvement in diet counseling is desired.

For children's food allergy, it must be kept in mind that allergic symptoms may occur at school. Networking among the school nurse, dietitian and physician plays an important role in emergency care.

Eliminating eggs, etc., from meals during pregnancy is not effective in preventing children's food allergy. Instead, expectant mothers should pay attention to good nutritional balance to prevent their own malnutrition. Weaning food should not be given too early. It is appropriate to start giving weaning food to a 5-month-old or older baby whose digestive function may be ready.