Food allergy in children and adults with emphasis on peanut. Relation to IgE antibodies, food consumption, symptoms and disease development

Sammanfattning: Peanuts have been reported to cause severe allergic reactions especially in young children, and sensitisation present in small children suggests possible sensitisation in utero or during breast feeding. Some countries are therefore recommending maternal avoidance of peanut for the mothers during this period. Aims: To study the compliance of primary prevention advice distributed through Child Health Centres with emphasis on the introduction of food in families with stated hypersensitivity (I); to evaluate peanut sensitisation in a regional register material of serum tests for peanut during the period 1994-98(II); to study young individuals with peanut specific IgE antibodies in relation to age, peanut consumption and reported symptoms compared to 5 years previously (III); and to develop and evaluate recipes with high peanut content for Double Blind Placebo Controlled Food Challenge (DBPCFC) for diagnosing peanut allergic subjects. To study the availability of peanut protein in the recipes.The recommendation for introduction of foods during the first 12 months was followed for most parents except for gluten containing food. As many as 45 % waited to introduce gluten until 6 months or later which is more in line with previous recommendations. Among parents with hypersensitivity, only 23 % had waited to introduce egg and 33 % to introduce fish. Around 50 % of all mothers had avoided peanuts during pregnancy and lactation. There was nearly a three-fold increase in testing for peanut hypersensitivity during the studied period. There was also an increased amount of positive tests, from 34 % in 1994 to 45 % in 1998, suggesting an increased rate of peanut sensitisation. As many as 75 % of the tests with IgE antibody class 3 or more were children less than 10 years of age. Nearly 40 % showed a decreased IgE antibody level and 12 % reported tolerance to peanut during the follow up. Children 6 years or more at first test were more likely to show a decrease in peanut specific IgE level compared to younger children, independently of reported peanut consumption. Exposure to peanut, deliberate or undeliberate, was also more common in subjects with initially low IgE antibody level to peanut, as well as fewer reported symptoms during the study. Some of the subjects were sensitised without ever having any known reaction to peanut, and the children and their parents felt insecure how to handle the information about peanut sensitisation. A double blind chocolate recipe with up to 15 % content of peanut was developed and evaluated by sensorial test panels. In comparison with the only published recipe found, the developed recipe with high peanut content had no significant peanut taste as tested by the panels. There was less allergen available in the developed recipe with high fat content compared to the published recipe with low fat, measured by an inhibition method. As a second step, a validated double blind recipe with low fat content was developed.In conclusion: Avoidance of peanut during pregnancy is common among mothers. Peanut sensitisation seems to be present in many children and adults in Sweden as found in countries with a high peanut consumption. The results also indicate the difficulties in predicting a lower cut off value where subjects are likely to be free of symptoms. The diagnosis of food allergy should be based on both case history, IgE sensitisation and preferably confirmed with food challenge procedures. A test result without clinical data on the patient can lead to unnecessary anxiety and avoidance behaviour in some patients. As a tool for extended diagnosis and to simplify the standardisation of preparing DBPCFC, we have developed suitable recipes with documented availability as shown by an in vitro method.