Children who live with cats and dogs when they are infants are less likely to develop allergies later in childhood — and the more pets they have, the better, a Swedish study of 1,278 children has found.
Researchers interviewed the parents of 249 of the children when they were 6 to 12 months old, gathering information on pet ownership, and had clinical evaluations done at 18 months, 3 years and 8 to 9 years. The remaining families completed questionnaires on pet ownership and on the incidence of asthma, eczema and allergic rhinoconjunctivitis, the runny nose and itchy eyes that can occur when exposed to an allergen.
In both groups, allergy reports declined steadily with the number of pets, from about a third of the children in families with no pets down to zero in households with five or more cats or dogs.
The study, in PLOS One, controlled for many factors, but the link between pet ownership and decreasing risk for allergy persisted.
The lead author, Bill Hesselmar, an associate professor at the University of Gothenburg, said that having pets is only one factor in reducing the risk for allergy. Having more siblings and being born vaginally also reduce the risk.
“This is the hygiene hypothesis at work,” he said. “Even sucking on a pacifier and then giving it back to the kid produces a reduced risk for allergy.”