Research indicates that exposure to pets in early childhood is associated with a decreased likelihood of developing allergies such as asthma, hay fever, and eczema. A study led by Bill Hesselmar at the University of Gothenburg, Sweden, examined whether having multiple pets enhances this protective effect.
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The analysis included data from two previous studies. The larger study involved 1,029 children aged seven to eight. Among those who spent their first year of life in pet-free homes, the allergy incidence was 49 percent. This figure dropped to 43 percent for children who lived with one pet and to 24 percent for those who had three pets. Notably, two children who resided with five pets had no allergies.
The second study tracked 249 children from birth. After eight or nine years, it found that the allergy rate was 48 percent among those with no pet exposure during their first year, 35 percent for those with one pet, and 21 percent for those with two or more pets.
These findings suggest a dose-dependent relationship: as pet exposure increases, the risk of allergies decreases. Hesselmar noted that previous studies showing no link may have involved pets that were rarely in close contact with children. This rules out the possibility that families with allergies might simply choose not to own pets.
Furthermore, previous research has shown that children raised on farms with livestock have lower allergy rates. Hesselmar suggests that having multiple pets may create a similar environment, providing ample exposure to allergens.
Although allergies have increased since the mid-20th century, their exact causes remain unclear. Hesselmar posits that pets may carry microbes that help stimulate the human immune system, contributing to reduced allergy development. Additionally, spending time with peers and being outdoors in early years may also offer protective benefits.