Cohort study of peanut and tree nut sensitisation by age of 4 years.

OBJECTIVE

To determine the prevalence of sensitisation to peanuts and tree nuts in all children born during one year in one geographical area.

DESIGN

Birth cohort study with structured review at ages 1, 2, and 4 years.

SETTING

All children born on the Isle of Wight between January 1989 and February 1990.

SUBJECTS

Of 1456 children originally included, 1218 were reviewed at age 4 years. Of these, 1981 had skin prick tests.

MAIN OUTCOME MEASURES

Positive skin test results, clinical atopic disease, and risk factors for the development of atopy.

RESULTS

15 of 1218 (1.2%) children were sensitised to peanuts or tree nuts (13 to peanuts). Six had had allergic reactions to peanuts (0.5% of the population), one to hazelnuts, and one to cashew nuts; three had had anaphylactic reactions. Seven children had positive skin test results or detectable IgE to peanuts without clinical symptoms. Two children who reacted to peanut in infancy had lost their sensitivity by 4 years. Family history of atopy, allergy to egg (odds ratio 9.9, 95% confidence interval 2.1 to 47.9, and eczema (7.3, 2.1 to 26.1) were important predictors for peanut allergy.

CONCLUSIONS

IgE mediated allergy to peanuts is common in early childhood. In many the allergy persists but a minority may develop tolerance.