In addition to genetic factors, exposure in early childhood to house-dust mite allergens is an important determinant of the subsequent development of asthma.
SUBJECTSOne hundred babies were selected for the study before birth on the grounds that one parent gave a history of hay fever or asthma. This selection was designed to provide a cohort of children of whom, on the assumption of an autosomal dominant inheritance, half would be expected to develop evidence of atopy, those without atopy acting as controls. In this study a stringent definition of atopy was taken as the presence of one or more positive skin prick tests (¢4 mm weal diameter) to common allergens. The study had the approval of the health district ethical committee. After full explanation, written consent was obtained from the pregnant mothers. All the babies were born in the maternity department of Poole General Hospital during 1977 and 1978. The cohort of 100 babies was initially studied for five years and later restudied when aged 11 years when all except one were prepubertal. As most of the families continued to live in the area served by the hospital there remained 92, 73, and 67 children in the cohort at 1, 5,7 and 11 years respectively. The results presented in this report are on those 67 remaining children. Recurrent wheezing in childhood has a strong association with atopy and this genetic abnormality is one of the strongest risk factors predicting whether a child develops asthma.5 6 In an attempt to learn more of these variables we have conducted a prospective study from birth to 11 years in a cohort of children at risk of developing atopy. The study represents the METHODS All children were examined annually for their first five years and again when aged 11. The presence of eczema and wheeze was confirmed in all cases by a research nurse, a specialist, or a general practitioner during the first five years. A diagnosis of eczema was made when the skin of the face or of the flexures showed roughening, redness, or pruritus that persisted for four weeks or more. Hay fever was regarded as present if nasal discharge occurred in at least two spring or summer seasons. At the age of 11 years the diagnoses of hay fever and wheeze were based on a questionnaire administered to the patients inquiring into symptoms over the previous year and six years, while that for eczema was clinically confirmed.Bronchial responsiveness to inhaled histamine was assessed at the age of 11 years in 66 children using the deVilbiss method.'0 After a saline challenge, increasing doubling doses of histamine were administered, followed at one minute by measurements of forced expiratory volume in one second (FEV1) using a Vitalograph spirometer.
Breast feeding was associated with an increase in the prevalence of positive results from skin tests but was not associated with detectable IgE antibody to both food proteins, a lower concentration of IgG antibody to cows' milk, and was not associated with protection against the development of disease. A high level of exposure to dust mite was associated with an increased prevalence of positive results from skin tests to dust mite and appreciably higher antibody concentration.This study indicates differences in the humoral responses to food and inhalant allergens. Environmental factors appear to influence the development of these responses.
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