How many of us suffer from allergy to some substance? It could be anything, from egg or prawns to nuts or flowers. For instance, in the popular television sitcom The Big Bang Theory, one of the central characters Howard Wolowitz is allergic to something as trivial as peanuts. What is an allergy? How does one thing reduce an individual to a sneezing, wheezing, watery-eyed mess covered with skin rashes?
We all know that the immune system of the human body acts against a foreign substance, possibly a trouble-causing agent also known as an antigen and tries to eliminate it or neutralise it. In an immune response against an antigen, the immune system usually dispatches an army of molecules, some of which are antibodies. These molecules in the usual course of action against the intruder cause a minor inflammation in the affected area of the body. Most of the time, this inflammation is not severe and doesn’t result in damage of cells and tissue of the body. However, certain immune responses may elicit an inflammation which causes severe tissue damage and sometimes even death. Such inappropriate immune responses are termed as hypersensitivity reactions or more commonly called allergies.
This inappropriate response by the immune system was discovered early in the 20th century by two French scientists, Paul Portier and Charles Richet. They encountered people developing a bad reaction to jellyfish toxin while bathing in the Mediterranean. To counter this reaction they isolated some of the toxin and injected it in dogs as a vaccine against any future exposure to the toxin. However, their experiment met with disastrous results as the dogs exhibited a range of symptoms indicating a hyper reaction by the immune system against the toxin which was fatal. Portier and Richet then coined the term ‘anaphylaxis’ which can be loosely interpreted in Greek as the opposite of prophylaxis (prevention).
Allergies or hypersensitivities are of two types; immediate and delayed. As the name suggests, this classification is based on appearance of the symptoms of the inappropriate immune response against an antigen. The substance which stimulates the inappropriate immune response is called an allergen. Allergens can be several factors exposed to the human body by the environment. These allergens can be airborne, waterborne, part of food consumed and even components of some medicines, insect stings or different nuts. Reactions to these allergens include coughing, sneezing, watering or reddening of eyes, rashes on skin (hives), breathlessness, diarrhoea, vomiting and so on. Asthma is the most prevalent form of allergy all over the world. It is characterised by difficulty in breathing due to constriction or blockage of air passages of the body as a part of the inappropriate immune response to certain airborne allergens. If not rectified, this can even lead to death of individual. Often, it is treated by administering epinephrine which reverses the elicited immune reactions and prevents the resulting discomfort.