Pollens are most plentiful in the spring, so staying indoors and keeping windows closed will keep them out. Molds are often plentiful in the fall. As for indoor allergens, dust mites are the most common. They tend to hang out in bedding, so encasing beds and pillows in hypoallergenic coverings will reduce your exposure. Removing carpets, drapes and other furnishings that gather dust will further reduce the amount of dust you're exposed to.
Most experts recommend washing bedclothes once a week.
Because dust mites thrive in humid environments, using a dehumidifier to bring the humidity in your house to under 50 percent may also help. If you don't want to get rid of your pet, washing your cat, keeping him or her out of the bedroom, and using an air filter may be somewhat effective. Cockroaches can be battled with roach traps and sprays. Indoor molds can be found in bathrooms, basements, and other damp parts of the house. Housecleaning, which seems like the key to eliminating indoor triggers, is often a trigger itself because it stirs up dust and involves strongly perfumed cleaning solutions.