Your pet's dead skin flakes, urine, feces, saliva and hair can trigger asthma. Dogs, cats, rodents (including hamsters and guinea pigs) and other mammals can trigger asthma in individuals with an allergic reaction to animal dander. Proteins in the dander, urine or saliva of warm-blooded animals (e.g., cats, dogs, mice, rats, gerbils, birds, etc.) have been reported to sensitize individuals and cause allergic reactions or trigger asthma episodes in individuals sensitive to animal allergens.
The most effective method to control animal allergens in the home is to not allow animals in the home. If you remove an animal from the home, it is important to clean the home (including floors and walls, but especially carpets and upholstered furniture) thoroughly.
Pet allergen levels are reported to stay in the home for several months after the pet is removed even with cleaning. Isolation methods to reduce animal allergen in the home have also been suggested by reputable health authorities (e.g., keeping the animal in only one area of the home, keeping the animal outside or ensuring that people with allergies or asthma stay away from the animal) but the effectiveness of these methods has not been determined. Several reports in the literature indicate that animal allergen is carried in the air and by residents of the home on their clothing to all parts of the home, even when the animal is isolated. In fact, animal allergen is often detected in locations where no animals were housed.
Often, people sensitive to animal allergens are advised to wash their pets regularly. Recent research indicates that washing pets may only provide temporary reductions in allergen levels. There is no evidence that this short term reduction is effective in reducing symptoms and it has been suggested that during the washing of the animal the sensitive individual may be initially exposed to higher levels of allergens.
Thus, the most effective method to control exposure to animal allergens is to keep your home pet free. However, some individuals may find isolation measures to be sufficiently effective. Isolation measures that have been suggested include keeping pets out of the sleeping areas, keeping pets away from upholstered furniture, carpets, and stuffed toys, keeping the pet outdoors as much as possible and isolating sensitive individuals from the pet as much as possible.
Source: United States EPA
"Cats - a standing rebuke to behavioural scientists . . . least human of all creatures."