Prevention

People with existing allergies should avoid irritants or allergens. These triggers include:

Pollen. This is the primary cause of allergic rhinitis.
Dust mites, specifically mite feces, which are coated with enzymes that contain a powerful allergen. These are the primary allergens inside the home.
Animal dander (flakes of skin) and hair from cats, house mice, and dogs. House mice are proving to be significant sources of allergens, particularly in urban children.
Molds.
Fungi.
Cockroaches are major asthma triggers and may reduce lung function even in people without a history of asthma.
Some research suggests that alcohol intake may influence allergy severity. One study found that as little as one drink a day is enough to worsen dust mite allergies.
Some studies suggest that early exposure to some of these allergens, including dust mites and pets, may actually prevent allergies from developing in children.

Indoor Protection Against Allergens

Some experts believe that reducing the risk factors for asthma in the home could reduce asthma in children by as much 40%.

Controlling Pets. People with asthma who already have pets and are not allergic to them are probably at low risk for developing such allergies later on. When children are exposed to more than one dog or cat during their first year, they have a much lower risk for not only pet allergies but also seasonal allergies and asthma. (Pet exposure does not protect them from other allergens, notably dust mites and cockroaches).

In children who have an existing allergy to pets, however, the pets should be given away or kept outside. If this isn't possible, they should at least be confined to carpet-free areas outside the bedroom. Cats harbor significant allergens, which can even be carried on clothing. Dogs usually present fewer problems. Washing animals once a week can reduce allergens. Dry shampoos, such as Allerpet, that remove allergens from skin and fur and are now available for both cats and dogs and are easier to use than wet shampoos.