Allergic reaction
The term ‘allergy’ was first coined in 1906 by Viennese doctor Clemens von Pirquet, who put together the Greek words alios (meaning ‘different’) and ergon (‘work’). It is believed he meant that the allergic reaction was caused by something working differently from normal.
As with all hypersensitivity reactions, the culprit substance must gain access to the human body for the backlash to occur. Contact with such a substance can come about in the following ways:
• through the skin
• via lung inhalation
• from touch.
Mounting an attack
People who are not susceptible to allergens experience no adverse reaction after exposure to them. However, inside the body of a person who is susceptible a type of war takes place. Believing it is being invaded by a foreign substance, the body’s immune system triggers the production of masses of protective antibodies called immunoglobulin E (IgE for short) to mount an attack on the invaders. We all have a number of IgE defenders whose aim it is to fight off invaders, but people who are allergic to certain substances produce too many for their own good when provoked. The result of this sudden overabundance is termed a ‘systemic inflammatory response’, which means that one of the body’s systems – the upper respiratory system, where hay fever is concerned – becomes swollen, reddened, hot and often painful. This response manifests itself as the runny nose, watering eyes and so on that we associate with hay fever.
Allergies to other substances may be so severe that they can result in life-threatening anaphylactic shock – an extreme allergic reaction where the blood pressure suddenly drops and there is difficulty breathing. Left untreated, it can even lead to death. Fortunately, an allergy to pollen and the other allergies encompassed in the umbrella term allergic rhinitis is not life-threatening.
There is, as yet, no absolute cure for allergic reactions of any kind. The best treatment of all is avoidance, but this is not always possible.
Hypersensitivity
Until a few decades ago, all types of hypersensitivity were considered to be allergies and believed to be caused by the inappropriate activation of immune system antibodies. These days we know that several different mechanisms are involved in what are now described as ‘hypersensitivity reactions’, and a new classification has been set up.2 Under the new classifications, a true allergy is restricted only to ‘hypersensitivity reaction type T, which means that it gives rise to a more severe reaction than in lower classifications of hypersensitivity.
Any hypersensitivity provokes mistaken activation of immune system antibodies, caused by an acquired sensitivity to a substance that would be seen as innocuous to a healthy immune system. Obviously, not all substances set up hypersensitivity reactions, but the ones that do include pollen, dust, yeasts, animal fur, bee venom, house dust mite dung, certain foods and certain drugs.