Is there really a hypoallergenic dog?

Unfortunately, no -- all dogs can trigger allergic symptoms in a sensitized person.  However, there may be other things one can do to limit the amount of exposure in homes with pets.

What influences the amount of dog allergen in homes?  It seems obvious that there would be more dog allergen in a bedroom if pets are allowed in the room, and there would be even less dog allergen in the home if pets are kept outdoors or there are no pets at all.  However, does the type of coat make any difference?  How much the dog sheds?  How many dogs are in the home? How long the family has had the pet?  How many hours the dog spends in the home?  The size of the dog?  Whether the pet is altered (spayed or neutered)?

As it turns out, the type of dog coat, amount of shedding, and number of dogs in the home make no difference in the amount of dog allergen in the home.   However, the amount of time there are dogs in the house does correlate with dog allergen levels in the home, and the larger the dog, the higher the allergen levels.  For unknown reasons, spayed or neutered dogs seemed to release more allergen than unaltered dogs.

Ann Allergy Asthma Immunol 2010;105(3):228-33.  Nicholas C, Wegienka G, Havstad S, Zoratti E, Ownby D, Johnson CC.  Dog characteristics and allergen levels in the home.