Allergies are hypersensitive immune responses to things that are generally not harmful, such as pollen, cat dander, or certain types of foods. If you are going to develop an allergy, you must first be exposed to something for which you are predisposed to develop an allergy (this trait is generally inherited from your parents). Once exposed, the body goes through a complex set of reactions in preparation for a second exposure. This is very similar to getting the flu. Once you catch a particular type of flu, the immune system learns how to identify it and to fight it off so that the next time you are exposed to it, in most healthy people, it is nearly impossible to catch the same type of flu a second time. Now just as with fighting the flu, when you develop an allergy, the body creates cell surface markers which attach to mast cells or basophils, and are used to recognize the allergens next time you are exposed to them. However there are a few differences between the way the body responds to viruses and bacteria and the way it responds to allergens. These differences will be explained next.
The members of the immune system that guard your body against foreign substances such as bacteria, viruses, and other toxins, are called Lymphocytes. The job of your lymphocytes is to travel through the blood checking every cell in your body to be sure that non of them are posing any threat to any other part of the body. If these lymphocytes find a molecule that has a surface marker identifying it as a foreign invader, after having come in contact with this invader, the lymphocyte returns to the lymph node, changes into a plasma cell, and produces antibodies. These antibodies attach to basophils and mast cells and are used to recognize things that do not belong. Once the antigen is meets an antibody, the fight against the bacteria or virus begins.
Now, when lymphocytes mistakenly label a benign substance as a threat, the body responds by producing a certain type of antibody (called an IgE protein) to identify this allergen upon repeat exposure. These antibodies attach to mast or basophil cells with the intent of identifying the particular allergen. Now once exposed a second time, the allergen is sought out by the antibody protein and attaches to it. Then additional complement proteins attach themselves to the foreign object, forming a chain sequence that eventually destroys the cell with the allergen attached. This is fine when the cells that are being destroyed are diseased cells. But when it is a mast cell or a basophil that is being destroyed, upon their destruction, a large amount of histamine is released. Histamine causes blood vessels to become dilated and blood pressure to drop below normal. The spaces between the surrounding cells fill with fluid, and the body begins to exhibit physical symptoms to rid itself of the foreign object. Common allergy symptoms include sneezing, wheezing, hives, itching of eyes, nose or other parts of the body, and sometimes even diarrhea or vomiting.
In rare cases, but still important enough to discuss, allergic reactions that involve the entire body are called anaphylaxis. This is when the blood vessels all over the body begin to dilate to the point of extreme danger. If the fluid which begins to form in response to the histamine, congregates around the tissues of the throat, the throat can swell shut and cause death in as little as 3 minutes after exposure. This is considered anaphylactic shock. The only way to treat this type of shock is with a shot of epinephrine (synthetic adrenaline). This will open the bronchial tubes to allow normal breathing to resume.
Now that you understand what an allergy is and how the body responds once exposed to an allergen, how do you protect yourself from an allergic response? Well one thing is to be sure that your immune system is in top shape. When your immune system is compromised, the lymphocytes tend to have difficulty distinguishing between threatening and non-threatening elements. So make sure that your body gets plenty of nutrients and exercise, but also cleansing your body and drinking plenty of water will help flush the body of toxins and foreign matter.