Types of Asthma

Asthma is a common chronic inflammatory condition that affects the airways of the lungs.

Unfortunately it is one of the many medical conditions that remain a mystery and as yet it is still not completely understood. There are three main characteristics that help to diagnose asthma:

* The hyper-responsiveness of the small airways within the lungs, such as the bronchi, to a number of common stimuli including allergens and irritants like pollen, cigarette smoke, dust mites, food ingredients, and perfumes.
* Inflammation of the bronchi. The bronchi are the tiny tubules within the lungs which allow air and oxygen to reach the bloodstream. When they become inflamed as a reaction to a specific allergen or irritant they swell shut so that it becomes much more difficult for air to pass through them.
* Airflow limitation because of inflammation that is normally reversible either spontaneously or with medication.

Asthma can be divided into two main categories:
1. Extrinsic – this is where a definite external cause can be discerned, such as the common stimuli mentioned above.
2. Intrinsic or Cryptogenic – this is when no causative agent can be identified.

Over 90% of children and around 50% of adults with persistent asthma are found to have the extrinsic type and simple skin prick tests can normally pinpoint the allergens to which they are allergic. People with the intrinsic type are tested for all of the common allergens and irritants but none of them are found to trigger an asthmatic episode. In these cases the patient is advised to keep a strict journal detailing where they were and what they were doing immediately before an asthmatic episode so that links can be formed and potential allergens can be identified.

Asthma can also be classified according to when the patient first started showing symptoms - early onset in childhood or late onset during adulthood. These two divisions often have different causes and these will be discussed in the following section.