What Is The Cause Of Asthma?

Something yet 'unknown' that primarily has to do with the human immune defense system is what causes asthma. Asthma is mainly an inheritable disease and runs in families. Genetics and hereditary factors that cause abnormal behavior of the immune defense system sum up in short the cause of asthma.

Certain completely unconnected allergens (specific triggers) and irritants (non-specific triggers) become the causative agents for the occurrence of asthma in some individuals. At the same time, other individuals are not affected by any of these triggering agents and so in them asthma does not occur.

In asthma prone individuals, a structural abnormality in their immune defense system causes it to consider the triggers entering the body through breathing as foreign bodies. As a result the immune defense system takes over. It causes mast cells lining the bronchial airways to release certain substances known as histamines and leukotrienes.

Their release is an indication for the entry of white blood cells into the area. These cells invade the 'triggers'. The bronchial airways swell and get inflamed due to this action of the white blood cells. Furthermore, extra mucus is secreted by the cells lining the airways. Another aspect of the immune defense mechanism that plays a role here is that the muscles surrounding the airways go into contraction.

The airway passage then becomes constricted partly due to muscular contraction, partly due to inflammation and swelling of the airway wall and partly due to extra mucus blocking the passageway. This causes bronchiole obstruction of the passageway which in turn causes the characteristic difficulty in breathing due to asthma.

Th2 cells that are a subgroup of helper T cells, a category of white blood cells are suspected of playing a central role in the mechanism by which asthma attacks occur in individuals. These cells produce interleukins that in turn stimulate the overproduction and release of immunoglobin E (IgE). It is this IgE that binds to mast cells and brings about the release of histamine and leukotrienes.

Different individuals are affected by different causative triggers. Some are affected by pollen, some are affected by dust mites and dust mite feces, and some others are affected by air pollution. Some others are affected by pet dander and cockroach droppings. Asthmatic attacks occur after individuals inhale one of these allergens.

Irritants in the environment such as cigarette smoke, wood fires, paint fumes, perfumes, gasoline, and scented soaps can also cause asthma. Primarily, these do not cause asthma, but they can aggravate already inflamed and sensitive bronchial airways. Passive smoking can also aggravate asthma in individuals.

Besides these, certain respiratory infections that include flu, colds, sore throats, and sinus infections can also be triggering mechanisms for asthma. Exercise, especially a vigorous and sustained one done in cold weather can also trigger an asthmatic attack.

Research is still going on as to exactly what causes asthma. Let us hope the picture becomes clearer in the near future.

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