Over the years, the medical profession has developed several ways of classifying asthma and of distinguishing one form of the disease from another. Let's take a look at some of these classifications now. Traditionally, doctors have separated asthma into two general categories, extrinsic asthma and intrinsic asthma, depending upon the types of stimuli that trigger episodes of the disease.

What is extrinsic asthma?

Asthma triggered by allergies is known as extrinsic asthma. It is also called allergic or atopic asthma. In this form of the disease, an asthma attack is clearly linked to the body's response to something inhaled or, occasionally, ingested. Substances to which the person is allergic are called allergens.

What sorts of things can be allergens?

The most common allergens are tree and grass pollen, mold, animal dander and dust mites.

Who develops extrinsic asthma?

Asthma that develops in childhood is likely to be extrinsic. More than 90 percent of asthmatic children under age 16 have allergies, as do 70 percent of asthmatic people ages 16 to 30, according to the National Institute of Allergy and Infectious Diseases . Symptoms of extrinsic asthma often vary seasonally and occur intermittently. In more than half the cases of extrinsic asthma, there is usually a personal or family history of other allergies, such as hay fever and skin conditions.

What is intrinsic asthma?

Asthma that develops in people over the age of 30 is usually intrinsic or nonallergic asthma. As the names imply, this asthma is not allergy related.

What is it related to?

It is related to triggers such as respiratory infections, exercise, stress, inhalation of chemical irritants (such as cleaning fluids or fresh paint) and air pollution. While doctors believe that extrinsic asthma is caused by an overactive immune system, they do not yet understand the origins of intrinsic asthma.

Is it important to know which form of asthma I have?

Insofar it helps you understand your disease and suggests a path for medical treatment, yes. However, you should be aware that most people with asthma have both forms. For example, it is very common for someone with the extrinsic form of the disease to experience asthma attacks when she has a cold or the flu - both intrinsic triggers.

Extrinsic and intrinsic are two terms that attempt to describe the source and trigger of the asthma. Other types of asthma have been named after the particular situations in which they occur, such as nocturnal asthma, seasonal asthma and exercise-induced asthma.