Asthma
Asthma is a chronic disease that affects about 20 million Americans. Its primary cause is inflamed airways in the lungs. This inflammation makes the airways smaller, which makes it more difficult for air to move in and out of the lungs.
Signs that you might have asthma include:
Many people have "allergic asthma," which means that allergens - like dust mites, mold, animal dander, pollen and cockroaches - make their symptoms worse.
Other things that can affect adult asthma include:

Common Indoor Asthma Triggers:
The more the asthmatic person is exposed to these triggers, the more inflamed their airways become compared to the normal airway. To promote the best breathing possible and to prevent asthma attacks, avoid triggers!
Secondhand smoke: This is a mixture of smoke from the burning end of a cigarette, pipe, or cigar and the air exhaled by the smoker that is often found in homes and cars where smoking is allowed.
Dust mites: Dust mites are too small to be seen, but can be found in almost every home in mattresses and bedding materials, carpets, upholstered furniture, stuffed toys, and curtains.
Mold: Mold can grow indoors when mold spores land on wet or damp surfaces. In the home, mold is most commonly found in the bathroom, kitchen and basement.
Cockroaches and Other Pests: Cockroach body parts, secretions and droppings, and the urine, droppings and saliva of pests, such as rodents, are often found in areas where food and water are present.
Warm-Blooded Pets: Pets' skin flakes, urine and saliva can be found in homes where pets are allowed inside.
Nitrogen Dioxide: Nitrogen Dioxide is a reddish-brown, irritating odor gas that can be a byproduct of indoor fuel-burning appliances, such as gas stoves, gas or oil furnaces, fireplaces, wood stoves, and un-vented kerosene or gas space heaters.