Allergy

An allergy or Type I hypersensitivity is an immune malfunction whereby a person's body is hypersensitised to react immunologically to typically nonimmunogenic substances. When a person is hypersensitised, these substances are known as allergens. The word allergy derives from the Greek words allos meaning "other" and ergon meaning "reaction" or "reactivity". Type I hypersensitivity is characterised by excessive activation of mast cells by immunoglobulin E resulting in a systemic inflammatory response that can result in symptoms as benign as a runny nose, to life-threatening anaphylactic shock and death.

Basis of the allergic response

Genetic Basis

There is much evidence to support the genetic basis of allergy, as allergic parents are more likely to have allergic children, and their allergies are likely to be stronger than those from non-allergic parents. However some allergies are not consistent along genealogies with parents being allergic to peanuts, but having children allergic to ragweed, or siblings not sharing the same allergens. Ethnicity has also been shown to play a role in some allergies. Interestingly, in regards to asthma, it has been suggested that different genetic loci are responsible for asthma in people of Caucasian, Hispanic, and African origins.

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Relationship with parasites

Some recent research has also begun to show that some kinds of common parasites, such as intestinal worms (e.g. hookworms), secrete immunosuppressant chemicals into the gut wall and hence the bloodstream which prevent the body from attacking the parasite. This gives rise to a new slant on the hygiene hypothesis - that co-evolution of man and parasites has in the past led to an immune system that only functions correctly in the presence of the parasites. Without them, the immune system becomes unbalanced and oversensitive. Gutworms and similar parasites are present in untreated drinking water in undeveloped countries, and in developed countries until the routine chlorination and purification of drinking water supplies. This also coincides with the time period in which a significant rise in allergies has been observed. So far, there is only sporadic evidence to support this hypothesis - one scientist who suffered from seasonal allergic rhinitis (hayfever) infected himself with gutworms and was

Related Topics:
Hookworm - Immunosuppressant

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immediately 'cured' of his allergy with no other ill effects. Full clinical trials have yet to be performed however. It may be that the term 'parasite' could turn out to be inappropriate, and in fact a hitherto unsuspected symbiosis is at work.

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