Maternal farm exposure/ingestion of unpasteurized cow's milk and allergic disease.

PURPOSE OF REVIEW: The prevalence of allergic diseases has reached a high prevalence in affluent countries. Yet, there are areas and living conditions associated with very low rates which are attributable to environmental exposures. One example is the low prevalence of childhood asthma and allergies amongst children raised on farms, particularly those exposed to farm animals and unprocessed cow's milk very early in life which are being reviewed in this article.

RECENT FINDINGS: Several studies have shown that maternal exposure to various farm animals in pregnancy is related to a reduced risk of atopic dermatitis in the child and immune responses which have generally been regarded as protecting from the development of asthma and allergies. In addition, maternal and infant consumption of unprocessed cow's milk has repeatedly been associated with protection from childhood asthma and allergies. The precise nature of the protective factors remains to be elucidated. Maternal exposures to farm animals result in increased microbial exposures, the diversity of which has been associated with protection from childhood asthma. The beneficial milk constituents may, however, not be contained in the microbial contamination of milk samples but rather in the whey fraction of unprocessed cow's milk.

SUMMARY: Better understanding of these protective exposures might in the future enable the development of new prevention strategies.