For children at higher-than-average risk of asthma, having a dog around the house may increase the chances of developing the lung disease, a new study suggests.
The study, which followed 380 children at increased risk of asthma due to family history, found that those exposed to relatively high levels of dog allergen at the age of 7 were more likely to have asthma.
In contrast, there was no relationship between cat-allergen exposure and a child's risk of asthma, according to findings published in the journal Pediatric Allergy and Immunology.
Exactly why dogs were related to a higher risk of asthma, while cats were not, is not entirely clear. But one factor may be endotoxin, a substance produced by bacteria that is known to trigger inflammation in the airways, explains lead researcher Dr Chris Carlsten, of the Vancouver General Hospital in British Columbia, Canada.
Carlsten and his colleagues found that children exposed to dog allergen at home were not at increased risk of developing an immune-system sensitization to dog allergen itself.