Early exposure to pets: good or bad?

Although pet exposure is known to trigger or worsen allergy symptoms and asthma in patients sensitized to pets, data from recent years has shown that pet exposure in early childhood may actually prevent the development of allergic sensitization and allergic diseases including allergic rhinitis, asthma, and atopic dermatitis. The concept of a protective pet effect remains controversial because these findings have not been duplicated in all studies. Moreover, some studies suggest that pet exposure promotes allergic disease.

The hygiene hypothesis revisited.

The original hygiene hypothesis proposed that reductions in family size and exposure to childhood infections were responsible for the rise in atopic diseases. Numerous epidemiologic and longitudinal studies have been performed to test this hypothesis, which has evolved in response to these findings and emerging concepts related to the innate immune response and immunoregulatory mechanisms. Collectively, these advances raise hope that the concepts espoused in original hygiene hypothesis may soon lead to new preventive approaches to atopic diseases.