CAUSE OF ALLERGY
To clearly explain what the cause of allergy is to you. Let me start with this one of the numerous examples of allergic reactions. A household animal, dog, was brought into a house. After three month the dog was brought in, mum begins to experience itchy nose and throat and episodes of sneezing. One of the children in the house also develops chest tightness and coughing, especially when the dog is in her bedroom. The rest of the household (dad and the rest of the children) have no reaction (allergy symptoms) to the presence of the dog irrespective of the degree of contact they have with the dog.What happened was that, mum and one of the children in the house (in which dog was brought) were allergic or developed allergy toward a foreign substance on or in the dog. Thus, the manifestation of the allergy symptoms in the mum and one of the children. Â But dad and the rest of the children are not allergic or did not develop allergy to the presence of the dog. Foreign substances (such as that from the dog) are called antigen. Antigens are substances capable of triggering or causing production of antibodies. The antibodies are produced from immune system. Immune system is a body's organised defence system against foreign invaders (antigens), especially infectious agents. Antigens may lead or may not lead to an allergic reaction and the consequent allergy symptoms. Any antigen that causes allergy symptoms (or allergic reactions) is referred to as allergen. The function of immune system in our body is to mobilize its defensive components to the site of invasion or infection in order to destroy the intruders, the foreign substance (antigen or allergen if it causes allergy or allergy symptoms). The immune system destroys antigens or allergens in two ways. When the immune system components have contact with the antigens or allergens, they respond by producing antibodies or immunoglobulins (Ig) - the first way. There are five types of these antibodies - IgG, Â Â IgM, IgA, IgD, and IgE. The function of the antibodies in the destruction of the invaders is to attach themselves to the surface of the foreign substances and thereby make the foreign substance easier for the immune cells to destroy- the second way immune system functions to destroy invaders.The function of the immune system described above is a normal process in everybody. In a person that is not allergic to an antigen, the antibodies are produced in normal quantities to successfully fight the foreign substance and there is no any development of any allergy symptoms. However in allergic person, IgE is produced in excessive amount in response to the same antigen and this result to the development of allergy symptoms.Not that the foreign substance or the antigen or the allergen will generally cause allergy in the human body, not that the substance is harmful by itself, it is just that in some people,Â in the process of immune systems getting rid of the antigens, there is overproduction of IgE antibody. Such people are said to be allergic to the substance. Overproduction of the IgE is called hypersensitivity.
A person who is allergic to an antigen or allergen doesn't start manifesting allergy symptoms or allergic reaction immediately he or she is exposed to the allergens for the first time. It takes times, months to years, before one starts showing the manifestation of the allergy symptoms. The period between the first exposure to the allergen and the manifestation of the allergy symptoms is called sensitisation period. During the sensitisation period IgE is being overproduced. Also during this period, as the IgE is produced, the IgE will be coating certain explosive cells that contain degrading chemicals. After the sensitisation period, another exposure to the allergen (such as dog dander or allergen cited above) leads to reaction of the allergen with the immune cells already coated or sensitised with IgE. This results into the cells releasing the various chemicals they contain, such as histamine. These chemicals, in turn, cause inflammation and the typical allergy symptoms. This is how the immune system becomes exaggerated and move to cause an allergic reaction when stimulated by an allergen in individuals which are allergic to the allergen. Â Â Â Â Â