An allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person’s immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid. Allergy is one of the four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity. Allergic reactions are distinctive because of excessive activation of certain white blood cells called mast cells and basophils by a type of antibody called Immunoglobulin E (IgE). This reaction results in an inflammatory response which can range from uncomfortable to dangerous medical conditions.
According to the leading experts in allergy, an allergic reaction begins in the immune system. Our immune system protects us from invading organisms that can cause illness. If you have an allergy, your immune system mistakes an otherwise harmless substance as an invader. This substance is called an allergen. The immune system overreacts to the allergen by producing Immunoglobulin E (IgE) antibodies. These antibodies travel to cells that release histamine and other chemicals, causing an allergic reaction.
Mild allergies like hay fever are very common in the human population and cause symptoms such as red eyes, itchiness, running nose, eczema, hives, or an asthma attack. Allergies can play a major role in conditions such as asthma. In some people, severe allergies to environment, diet or medicines allergens may result in life-threatening reactions called anaphylaxis. Food allergies and reactions to the venom of stinging insects such as wasps and bees are often associated with severe reactions.
Allergies are among the most common chronic conditions worldwide. Symptoms of allergies range from making you miserable to putting you at risk for life-threatening reactions.
An allergic reaction typically triggers symptoms in the nose, lungs, throat, sinuses, ears, lining of the stomach or on the skin. For some people, allergies can also trigger symptoms of asthma. In the most serious cases, a life-threatening reaction called anaphylaxis may also occur.
A number of different allergens are responsible for allergic reactions. The most common include:
• Insect stings
• Animal dander
Allergic Rhinitis: It is also known as hay fever or pollinosis. If you sneeze a lot, if your nose is often runny or stuffy, or if your eyes, mouth or skin often feels itchy, you may have allergic rhinitis. Allergic rhinitis, like skin rashes and other allergies, develops when the body’s immune system becomes sensitized and overreacts to something in the environment that typically causes no problem otherwise in most people. Allergic rhinitis takes two different forms:
• Seasonal:Symptoms of seasonal allergic rhinitis can occur in spring, summer and early fall. They are usually caused by allergic sensitivity to airborne mold spores or to pollens from grass, trees and weeds.
• Perennial: People with perennial allergic rhinitis experience symptoms year-round. It is generally caused by dust mites, pet hair or dander, cockroaches or mold. Underlying or hidden food allergies rarely cause perennial nasal symptoms.
Some people may experience both types of rhinitis, with perennial symptoms getting worse during specific pollen seasons. There are also non-allergic causes for rhinitis.
• Runny nose
• Itchy eyes, mouth or skin
• Stuffy nose due to blockage or congestion
• Fatigue (often reported due to poor quality sleep as a result of nasal obstruction)
• Outdoor allergens, such as pollens from grass, trees and weeds
• Indoor allergens, such as pet hair or dander, dust mites and mold
• Irritants, such as cigarette smoke, perfume and diesel exhaust
If you or your child have allergy symptoms, an allergist / immunologist, often referred to as an allergist, can help you with a diagnosis. An allergist has advanced training and experience to properly diagnose the allergy and help you feel better and live better.
Allergy testing involves having a skin prick test or blood test to find out what substance, or allergen, may trigger an allergic response in a person. Skin tests are usually done because they are rapid, reliable, and generally less expensive than blood tests, but either type of test may be used.
Allergy blood test identifies for substances in the blood called antibodies. Blood tests are not as sensitive as skin tests but are often used for people who are not able to have skin tests.
The most common type of blood test used is the enzyme-linked immunosorbent assay (ELISA, EIA). It measures the blood level of a type of antibody (called immunoglobulin E, or IgE) that the body may make in response to certain allergens. IgE levels are often higher in people who have allergies or asthma.
Other lab testing methods, such as Radioallergosorbent testing (RAST) or an immunoassay capture test (ImmunoCAP, UniCAP, or Pharmacia CAP), may be used to provide more information.
Advantages of blood tests for allergies
• They can be done at anytime, irrespective of any medications being taken
• They require only one needle prick for drawing blood.
• A small amount of blood drawn from the body can be used for performing multiple tests
A small quantity of a suspected allergen is placed on or below the skin to see if a reaction develops. There are three types of skin tests:
• Skin prick test:This test is done by placing a drop of a solution containing a possible allergen on the skin, and a series of scratches or needle pricks allows the solution to enter the skin. If the skin develops a red, raised itchy area (called a wheal), it usually means that the person is allergic to that allergen. This is called a positive reaction
• Intradermal test:During this test, a small quantity of the allergen solution is injected into the skin. An intradermal allergy test may be done when a substance does not cause a reaction in the skin prick test but is still suspected as an allergen for that person. The intradermal test is more sensitive than the skin prick test but is more often positive in people who do not have symptoms to that allergen (false-positive test results).
• Skin patch test:For a skin patch test, the allergen solution is placed on a pad that is taped to the skin for 24 to 72 hours. This test is used to detect a skin allergy called contact dermatitis.
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