Some people prone to allergies keep their homes pet-free, a study shows - but such "avoidance" of furry companions only partly explains the lower allergy risk found among pet owners.
The findings, published in the Journal of Allergy and Clinical Immunology, lend some support to the theory that growing up with a pet trains the immune system to be less reactive to potential allergy triggers.
A number of studies, for instance, have found that children exposed to a cat or dog early in life are less likely to develop allergies and asthma.
On one hand, this could indicate a protective effect of pets on immune system development. But an alternative explanation is that families with a genetic tendency toward allergies often opt for a pet-free home, whereas those with an inherently lower risk are more likely to keep pets.
To investigate this question, researchers used data from 9,812 European adults who took part in a 9-year study of respiratory health. Participants were asked about childhood allergy and asthma symptoms, as well as their exposure to pets throughout life.
The researchers found that when people developed allergies or asthma as babies or pre-schoolers, their families were less likely than others to get a cat or keep a cat they already had.
However, this was not true of families where a parent had allergies or asthma.
And while people with both current and childhood asthma were less likely to have a cat in adulthood, childhood symptoms alone did not prevent adults from getting a pet.
In general, adults who had pets before developing respiratory problems usually kept the animal, according to the researchers, led by Dr. Cecilie Svanes of the University of Bergen in Norway.
"People appear to prefer taking asthma medication rather than getting rid of a beloved pet," the researchers write, "which seems reasonable."
Like many previous studies, the current one found that pet owners had a lower risk of allergies - one third lower than that of their pet-free peers. But "pet avoidance" among allergy sufferers explained only part of this relationship.
"Thus," the researchers write, "although selective avoidance is certainly present, it appears to account for only a part of the protective effects of pets presented in the literature."
However, even if pets exert a true protective effect, experts don't recommend running out and buying a furry friend to prevent young children from developing allergies. If a child is already sensitive to pet dander, this will worsen the situation.
SOURCE: Journal of Allergy and Clinical Immunology, September 2006.
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