Which factors have been shown to reduce the prevalence of pediatric asthma?

Updated: Jan 08, 2019
  • Author: Girish D Sharma, MD, FCCP, FAAP; Chief Editor: Kenan Haver, MD  more...
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Answer

Evidence suggests that the prevalence of asthma is reduced in children who experience the following events:

  • Certain infections (Mycobacterium tuberculosis, measles, or hepatitis A)

  • Rural living

  • Exposure to other children (eg, presence of older siblings and early enrollment in childcare

  • Less frequent use of antibiotics, including in the first week of life [7]

  • Early introduction of fish in the diet [7]

Furthermore, the absence of these lifestyle events is associated with the persistence of a Th2 cytokine pattern.

Under these conditions, the genetic background of the child, with a cytokine imbalance toward Th2, sets the stage to promote the production of immunoglobulin E (IgE) antibody to key environmental antigens (eg, dust mites, cockroaches, Alternaria, and possibly cats). Therefore, a gene-by-environment interaction occurs in which the susceptible host is exposed to environmental factors that are capable of generating IgE, and sensitization occurs.

A reciprocal interaction is apparent between the two subpopulations, in which Th1 cytokines can inhibit Th2 generation and vice versa. Allergic inflammation may be the result of an excessive expression of Th2 cytokines. Alternatively, recent studies have suggested the possibility that the loss of normal immune balance arises from a cytokine dysregulation in which Th1 activity in asthma is diminished. [8]

Results of two recently reported cross sectional studies of children growing up on farms in Central Europe who were exposed to greater variety of environmental microorganisms showed an inverse relationship between microbial exposure and the probability of asthma. [9]


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