Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
In Reply: As Dr Ente points out, the hygiene
hypothesis provides a tantalizing framework to explain the increase in incidence
of allergic disease and asthma. At a simple level the observation that the
presence of domestic animals in the house is associated with a decreased prevalence
of sensitization could be seen as evidence supporting the hypothesis. Indeed,
the observations by Ownby et al that the effect requires more than 1 animal,
and that it has an effect on allergens in general, could fit with a nonspecific
effect due to endotoxin.1 However, other
studies show that the effect of cats is allergen specific when compared with
that of dust mites, and that the presence of a cat can decrease the onset
of asthma in preteenage children.2,3 This
evidence argues against a parallel with the early childhood effects of endotoxin.
Furthermore, direct measurements do not show that the presence of a cat increases
Platts-Mills TAE, Erwin E, Woodfolk J, Sporik R. Exposure to Pets in Childhood and Risk of Atopic Disorders. JAMA. 2003;289(7):841-843. doi:10.1001/jama.289.7.841-a