Article

Skin reactivity and number of siblings

University Children's Hospital, Munich, Germany.
BMJ Clinical Research (Impact Factor: 14.09). 04/1994; 308(6930):692-5. DOI: 10.1136/bmj.308.6930.692
Source: PubMed

ABSTRACT To investigate the relation between skin test reactivity in children and number of siblings.
Cross sectional survey among schoolchildren aged 9-11 years. Skin prick tests in the children and self completion of written questionnaire by their parents.
5030 children in Munich and 2623 children in Leipzig and Halle, Germany.
Atopic status assessed by skin prick tests.
After possible confounders were controlled for, the prevalence of atopic sensitisation decreased linearly with increasing number of siblings (odds ratio = 0.96 for one sibling, 0.67 for five or more siblings; P = 0.005). In atopic children the severity of the skin test reaction as assessed by the weal size was not associated with the number of siblings.
Factors directly or indirectly related to the number of siblings may decrease the susceptibility of children to become atopic. Thus, declining family size may in part contribute to the increased prevalence of atopic diseases reported in Western countries over the past few decades.

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    • "Following prior research on the hygiene hypothesis (Matricardi, 1997; Riedler et al., 2001; Shaheen et al., 1996; Strachan, 1989; von Mutius et al., 1994), four measures of microbial exposures were considered: household size, the number of infections experienced during the first year of infancy, the presence of older siblings, and household pathogen exposures. First, household size included persons present and persons absent from the household during the baseline survey in 1983. "
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    • "Since then, many epidemiological findings have supported this theory. For instance, living in a large family, attending day care early in life, and growing up on a farm or in a family with an anthroposophic lifestyle have shown to reduce the risk of asthma and allergies [13] [14] [15] [16] [17]. Recently, being exposed to food-borne and oro-fecal infections at early age was found to be associated with a decreased prevalence of hay fever and asthma [18]. "
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    • "Epidemiological studies have demonstrated that the prevalence of atopic diseases is increasing in industrialized countries with a ''western'' life style. Moreover, it was found that large numbers of siblings , especially when sharing bedrooms, or early entry into day care reduces the risk of IgE-mediated allergies (von Mutius et al, 1994; von Mutius et al, 1994; Strachan, 1997; Kramer et al, 1999). The data suggest that infections during early childhood reduce the risk of unwanted TH2 responses. "
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