Asthma

Asthma is a chronic (long-term) lung disease. It affects your airways, the tubes that carry air in and out of your lungs. When you have asthma, your airways can become inflamed and narrowed. This can cause wheezing, coughing, and tightness in your chest. When these symptoms get worse than usual, it is called an asthma attack or flare-up.

What causes asthma?
The exact cause of asthma is unknown. Genetics and your environment likely play a role in who gets asthma.

An asthma attack can happen when you are exposed to an asthma trigger. An asthma trigger is something that can set off or worsen your asthma symptoms. Different triggers can cause different types of asthma:

Allergic asthma is caused by allergens. Allergens are substances that cause an allergic reaction. They can include
Dust mites
Mold
Pets
Pollen from grass, trees, and weeds
Waste from pests such as cockroaches and mice
Nonallergic asthma is caused by triggers that are not allergens, such as
Breathing in cold air
Certain medicines
Household chemicals
Infections such as colds and the flu
Outdoor air pollution
Tobacco smoke
Occupational asthma is caused by breathing in chemicals or industrial dusts at work
Exercise-induced asthma happens during physical exercise, especially when the air is dry
Asthma triggers may be different for each person and can change over time.

The symptoms of asthma include:

Chest tightness
Coughing, especially at night or early morning
Shortness of breath
Wheezing, which causes a whistling sound when you breathe out
These symptoms can range from mild to severe. You may have them every day or only once in a while.