how astama is caused

Asthma is caused due to-

1) An inherited tendency to develop allergies.

2) Parents who have asthma

3) Certain respiratory infections during childhood

4) Contact with some airborne allergens or exposure to some viral infections in infancy or in early childhood when the immune system is developing.

Asthmatic symptoms occur due to-

1) Allergens from dust, animal fur, cockroaches, mold, and pollens from trees, grasses, and flowers

2) Irritants such as cigarette smoke, air pollution, chemicals or dust, compounds in home decor products, and sprays (such as hairspray)

3) Medicines such as aspirin or other nonsteroidal anti-inflammatory drugs and nonselective beta-blockers Sulfites in foods and drinks, Viral upper respiratory infections, such as colds

Hope this helps!