While some animals seem to be more tolerable than others, there are no dogs, cats or other furry animals that do not cause allergic responses. It makes no difference whether an animal has short hair, long hair or how much it sheds.

Cats cause more severe allergic reactions than other pets
The major cat allergen is an extremely potent one called Fel d1. Secretions from the sebaceous glands of the skin are the primary source of Fel d1, but it is also deposited on the fur through the saliva when cats clean themselves through the licking or self-cleaning process. Eventually the Fel d1 flakes off and becomes airborne to trigger the symptoms that characterize allergies to cats. Male cats generally produce more allergens than females do.

Dander
The problem is not with the pet's hair. It is the dander, or microscopic scales of dead skin (similar to, but much smaller than the dandruff on the human scalp) which pets are constantly shedding that is the cause. They are so tiny that you seldom, if ever, know that they are circulating in the air or laying on the furniture and carpets. Dander is a common culprit in allergies to dogs. A dog can be bathed up to twice weekly to try to alleviate the excessive dander production. Be sure though to use a medicated pet shampoo prescribed by a veterinarian and not an inexpensive alternative which can dry out your pet's skin and worsen the problem for the both of you. A non-allergic member of the family should brush the dog often, preferably outside.

Urine
Recent studies indicate that urine (protein), from cats and dogs as well as from ferrets, guinea pigs, hamsters, and mice, contain allergens which can also trigger allergic reactions.

Short-haired or long-haired dogs - Doesn't matter
All dogs – short-haired, long-haired, wire-haired, curly-haired, even hairless—are potentially allergic. Allergic reactions to dogs are not caused by the hair or fur but by dander (the tiny scales of dead skin) and by sebaceous and salivary gland secretions. Short-haired dogs can cast off as many allergens into the environment as long-haired ones do.

While it has recently been established that some dogs cast off more allergens than others, there are no non-allergenic dogs. The reason Yorkie dogs are thought to be "safe" is probably because they are shampooed and groomed regularly and therefore cast off less dander in the home.

Some people may have more problems living with a dog that shed hair profusely because of the excessive amount of loose hair contaminated by dried saliva and dander clinging to it shed from the pet onto the rugs, furniture and the dogs bedding and favorite lounging places. Frequent vacuuming are usually necessary, along with the use of a moist sponge, to pick it up.

People cannot be allergic to some breeds of dogs and not to others
The possibility of dog breed-specific allergens was first investigated many years ago, reports Dr. David Knysak of the Department of Medicine's Allergy Division of the University of Michigan Medical Center. Subsequent studies have determined both qualitative and quantitative variations in the antigen content extracts derived from different dog breeds, however, he adds, no breed-specific allergens have been found.