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


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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    • "There were no differences in prior mycobacterial exposure6), parasitic infestation34), living area, family history and obesity35) between the subjects with and without anti-HBs. However, the information on the other potential confounders such as the family size, birth order36) and the socioeconomic level was not collected in the present study. These factors are likely to have affected our findings. "
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    • "Some pollutants can either impair defense mechanisms in the airways rendering them more susceptible to viral and/or bacterial infection, or cause an immunological toxicity in the airways (Krishna et al 1995). Pollutants may also play a direct or indirect role in the pathophysiology and the development of allergic diseases (Cookson et al 1989; von Mutius et al 1994a; Hershey et al 1997; Matricardi et al 1997; Jarvis et al 1997; Bodner et al 1998; Krämer et al 1998; Shek et al 2001; Riedl and Diaz-Sanchez 2005) (Figure 2). More work is needed to identify which pollutants have an impact on human health and in which subgroups, and the mechanism for disease development. "
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