Choosing a breed dubbed "hypoallergenic" may not be enough to avoid triggering a dog allergy, researchers found.
Homes with a hypoallergenic dog were no less likely to have detectable levels of dog allergen or to have lower average levels of allergen than homes with a nonhypoallergenic breed, according to Charlotte Nicholas of Henry Ford Health System in Detroit and colleagues.
The findings did not differ based on whether the dog was allowed into the area where dust samples were taken, the researchers reported online in the American Journal of Rhinology & Allergy.
"Clinicians should advise patients that they cannot rely on breeds deemed to be 'hypoallergenic,'" they wrote. "Additional scientific investigation into dog-specific factors and whether hypoallergenic breeds truly exist is warranted."
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Although there is increasing interest in hypoallergenic dogs -- perhaps spurred by the selection of a breed touted as such (the Portuguese water dog) by President Barack Obama and his family -- there are few studies assessing whether those breeds actually produce less allergen.
To explore the issue, Nicholas and her colleagues turned to the Wayne County Health, Environment, Allergy, and Asthma Longitudinal Study (WHEALS), in which urban and suburban Detroit women were recruited during a second or third trimester prenatal visit.
Dust samples -- which were analyzed for the presence of Canis familiaris 1, the major dog allergen -- were collected from the floors of the babies' bedrooms at the one-month postpartum visit.
The researchers conducted an Internet search to identify hypoallergenic breeds, and included those listed in more than 25 percent of the references as hypoallergenic.
Nicholas and her colleagues then developed four classification schemes using combinations of purebred and mixed-breed dogs for the analyses on home allergen levels.
Overall, there were 173 one-dog homes included in the study, and 94.2 percent had detectable levels of Canis familiaris 1.
There were no significant differences for any of the four classification schemes in the percentage of homes with detectable allergen based on the hypoallergenic status of the dogs.
In homes where the dog was allowed in the baby's bedroom, allergen levels tended to be lower with hypoallergenic dogs, and in homes where the dog was not allowed in the bedroom, levels tended to be higher with hypoallergenic dogs, although none of the differences reached statistical significance.
The findings remained consistent after adjusting for whether the dog was allowed in the baby's bedroom, the dog's weight, length of dog ownership, the time the dog spent indoors, the floor surface assessed for dog allergen, and the home's location.
The authors acknowledged some limitations of the study, including the lack of information on the amount of time the dog spent in the baby's bedroom, the reliance on maternal report of the dog breed, and a sample size that was too small to conduct analyses of individual breeds.
In addition, they wrote, "collecting samples directly from the dog as opposed to from the floor of the baby's bedroom may have made our results more similar to the few in the literature; however, the goal was not to replicate these laboratory studies, but rather to learn if certain breeds of dogs were associated with lower levels of dog allergen in the home."