Keep a diary to track when and where allergy symptoms strike. That's the key to determining what provokes your allergies and whether they are caused by outdoor allergens, such as grass and ragweed pollen, or indoor allergens, such as cockroaches, dust mites, mold, and pet dander.

Limit your exposure

Once you know the cause, you can take steps to limit exposure. For outdoor triggers, keep the windows shut and stay indoors when pollen or outdoor mold is high. After going outside, wash to remove any lingering triggers. For indoor allergies, use an air conditioner or a dehumidifier to reduce humidity to below 50 percent. Remove carpeting from bedrooms, wash rugs and curtains often, and vacuum regularly, preferably with a model that scored well in recent Consumer Reports tests, such as the Hoover Wind-Tunnel or the Kenmore Progressive.