Being exposed to two or more dogs at home suggested a slightly protective, but not significant, effect on children's risk of developing eczema, said lead researcher Esmeralda Morales, M.D., Pediatric Pulmonary Fellow at the University of Arizona in Tucson.
The study included 486 children who had been followed since birth. The researchers asked their parents how many cats and dogs they had in the house at the time the child was born, and then followed up one year later to see which children had been diagnosed with eczema.
Of the 134 children with cats in the household, 27.6% had eczema by one year of age, compared with 17.8% of 286 children without cats. While exposure to cats increased a child's risk of eczema whether or not their mother had asthma, the effect was more pronounced in children whose mothers did not have asthma.
Previous studies have found that people with eczema have a higher chance of also having allergic conditions including hay fever and asthma.
"Other studies have found that having cats or dogs at home seems to be protective against allergic diseases, so we expected to have similar findings," said Dr. Morales. "Pets are a source of a compound called endotoxin, and if a child is exposed to endotoxin early in life, the immune system may be skewed away from developing an allergic profile."
It's possible that the children in the study who developed eczema at age 1 might end up having a reduced risk of asthma or other allergic diseases later in life, Dr. Morales noted. "The findings do seem to add more questions about pets and asthma and allergies," she said. "Since there are a lot of contradictory data out there already, clearly it's a topic that needs further research."