Allergy

An allergy is an immune system response to something which is not directly dangerous to the body. The term was coined by Viennese paediatrician Baron Clemens von Pirquet in 1906, from the Greek words allos meaning changed or altered state and ergon meaning reaction or reactivity. He observed the exaggerated immune responses of some of his patients, and concluded that they were a response to outside allergens such as dust, pollen, or certain foods.

The most basic allergy symptoms are similar to those of a common cold - snuffling, itchy eyes, and sneezing. An allergy can also cause skin rashes, hives or weals such as contact dermatitis or eczema; these are often caused in reaction to medications.

Hay fever is one example of a very common minor allergy - large percentages of the population suffer from hayfever symptoms in response to airborne pollen. Asthmaticss are often allergic to dust mites.

Most allergies are minor annoyances, but they are not something to take lightly. An allergy can also be extremely life-threatening if it is severe, causing anaphylactic shock and a total shutdown of the airways, circulation and every function of the body.

Treatment

The only known fundamental treatment for allergy is hyposensibilization. Other medication, such as by antihistamines and cortisone, has the effect of reducing the symptoms.

Allergy causation

Recent research has shed some light on the mechanism by which many allergies operate, but this is by no means the whole story; some causative factors and allergenic pathways have yet to be explained. One common mechanism seems to be that insufficient stimulation of the immune system at certain critical points in the development of the body leads to a surfeit of "proto-immune" cells which have not been activated by the presence of genuine invasive pathogens to become true antibodies. Once past puberty, the immune system becomes "fixed", with the majority of activated antibodies established such that everyday pathogens provoke no response. However the unactivated ones remain, waiting for a unusual and potentially more serious invader. Minor irritants, or even the body's own waste products, can then trigger an antibody reaction in these cells which then incorrectly become primed to recognise these minor irritants as major invaders. A further exposure to these irritants then provoke a substantial and unwarranted immune response from the incorrectly programmed antibodies. It is the symptoms of this exaggerated response that is seen as the allergic reaction.

Many common allergies such as asthma have seen huge increases in the years since the second world war, and many studies appear to show a correlation between this and our increasingly affluent and therefore clean lifestyles in the west. This is supported by studies in less developed countries that do not enjoy western levels of cleanliness, and similarly do not show western levels of incidences of asthma and other allergies. During this same period, air quality, at one time considered the "obvious" cause of asthma, has shown a considerable improvement. This has lead some researchers to conclude that it is our "too clean" upbringing that is to blame for the lack of immune system stimulation in early childhood. Many children have a natural tendency, for example, to consume soil - a practice that often provokes an equally natural tendency in parents to stop them. However, it appears that this may have a valuable function in priming the immune system, and is one way to ensure that allergies are less likely to develop in later life.