Thursday, October 4, 2012
The allergenicity of “hypoallergenic” dogs
It’s a primitive social urge in humans to interact with dogs. So much so that many people found to be clinically sensitive to dogs will own them anyway. In this context, it is not surprising that the search for dogs that elicit a minimal allergic response would claim so much energy, but are there such things as “hypoallergenic” dogs? Vredegoor et al. look at that question in this month’s issue (J Allergy Clin Immunol 2012;130:904-909.e7).
The authors examine levels of the primary dog allergen, Can f 1, in samples from dog fur and skin, and settled and airborne dust from “hypoallergenic” dogs (Labradoodles, Poodles, Spanish water dogs, and Airedale terriers), normal allergenic dogs (Labrador retrievers), and a variety of breeds and mixed breeds that made up the control group. Their results are paradoxical and even ironic.
Poodles and Labradoodles had the highest levels of Can f 1 in their coat and skin; Labrador retrievers had the lowest. Hair and dander shedding was highest from Airedale terriers. Vredegoor et al. report that environmental levels of Can f 1 were not significantly different between “hypoallergenic” dogs and their allergenic counterparts, though homes with covered floors had overall lower environmental levels than homes with exposed floors. The authors note that other identified canine allergens, such as Can f 2 and 3, were not screened due to lack of available methods for analyzing large sample sizes.
The authors also collected information from owners by administering questionnaires. Dog-allergic owners reported much fewer symptoms with the breeds thought to be hypoallergenic and did not report having different house-cleaning practices than non-allergic owners. It was noted that recent swimming by the dogs had an overall effect of lowering allergen levels and Vredegoor et al. speculated that this could contribute to the lower levels found in Labrador retrievers, which are frequent swimmers.
Vredegoor et al. conclude that there is no evidence that supports the label “hypoallergenic” with respect to dogs, so we asked the authors to comment on a possible explanation for the number of dog-allergic owners who reported experiencing fewer symptoms with certain dogs: Senior author Esmeralda J.M. Seegers-Krop replies, “We believe the health effects can be a kind of placebo effect in these people. It has been seen in cat allergic people as well (they report not to be allergic to their own cat but only to other cats).”