Many Babies Healthier in Homes With Dogs
Fewer Colds, Ear Infections in Infants With Dogs (Cats Help, Too)
Why Might Dogs Make a Difference? continued...
"The microbiome hypothesis is that early-life exposure to wide varieties of microbes lets them mix with the microbes in the gut and helps them keep the immune system from reacting against itself and causing autoimmune disease, or from reacting against stuff you should ignore and causing allergy," she says.
The hygiene hypothesis has indeed changed, says Anna Fishbein, MD, an allergy and immunology fellow at Northwestern University and now an assistant professor at the University of Maryland.
"It's become more complicated. It's no longer just getting exposed to the right number of microbes, but to good bacteria and viruses that alter the microbes in our intestines and protect us against both allergies and infections," Fishbein tells WebMD.
Dogs Not Good for All Kids
But one child's good microbes are another child's bad microbes, DeMuth warns.
"There is also an interaction between these microbes and an individual child's genetics," she says. "Certain people who have a dog in the house are protected against infections and allergies, but some are not. This is not a one-size-fits-all kind of thing."
Worst of all, DeMuth says, is for the family of a sickly or asthmatic child to bring a dog into a pet-free home in the hope that it might help.
"The absolute wrong thing is to put a dog in the house for kids with asthma," she says. "Yes, having a dog in the house early can protect against wheezing or respiratory infections. But this exposure has to happen very early in life."
What about parents who are themselves allergic to dogs or cats? Should they bring a pet into the home for the sake of their soon-to-be-born child?
"This is always a hard question," Bergroth says. "But it is important for the child that its parents can live happily in the home without symptoms."
The Bergroth study appears in the August 2012 issue of Pediatrics.