Why We Show Allergic Responses to a Particular Stimulus?
We often hear our friends saying- I m allergic to this or I am allergic to that. Do you know what an allergy is and why it happens? You might be responding very normally to 
a particular thing while someone around you might have started sneezing on exposure to that thing. To understand why it is so, we need to know how the immune system of the body works.
In our body, the blood has white blood cells which are part of the immune system of the body. These lymphocytes (WBC’s) scan the various proteins for their chemical signatures, to identify them as self proteins or foreign proteins. If it recognizes any invading protein, it converts itself to plasma cells in the lymph nodes and release antibodies.
These antibodies then destroy the foreign protein and save our body from any kind of infection. A person suffering from an allergy has a genetic defect in which the white blood cells (WBC’s) do not correctly identify the proteins and overreact to them. Now, when the allergen is identified, the lymphocytes release antibodies in huge numbers. But there is no protein to attach to, as there is no real threat to the body so these antibodies attach themselves to the mast cells containing histamine. Histamine is an anti-allergen and isolates the area from allergens. When the body is exposed to the same allergen again, these antibodies destroy the mast cells and enormous amount of histamine is released in the body.
How is this increased amount of histamine levels in our body related to the allergic reactions? Actually, this histamine only is responsible for redness of skin, swelling, itching or hives on exposure to the allergen. Blood vessels contract and the gaps left are filled with fluid causing soreness and puffiness which can sometimes even prevent sight, breathing, hearing and makes movement uncomfortable and sometimes even impossible. Air-borne allergen causes breathing problems as the lungs and the respiratory tract contracts. Entry of allergen through blood is even more severe as blood travels the whole body within 5- 6 minutes. Thus, every organ of the body comes in contact with the allergen immediately and shows elevated reactions.
