The word asthma means "shortness of breath".
Asthma is an inflammation of the airways that can be caused by an allergy to various substances, in which case it is known as allergic asthma.
The inflammation can also result from an infection of the airways or from exposure to irritants, in which case it is known as non-allergic asthma.
Chemicals, particles (of dust or pollen, for example) and physical exertion can all bring on asthma.
If you frequently spend time in an environment which contains things that you are allergic to, or which has a high content of chemicals, particles or other irritants, there is a risk that the inflammation of your airways will become permanent.
If you have asthma, your airways will react more readily than normal to irritants. The symptoms are shortness of breath and coughing, often violently.
You won't necessarily develop problems immediately after coming into contact with an irritant. You may, for example, cough during the night after having been exposed to a substance you are allergic to during the day.
Your lungs may not function as well if you frequently cough and find it hard to breathe. You should therefore adopt a preventative approach to problems that recur frequently. Exercise will help - while smoking, for example, will make your asthma worse.