Allergy is a disorder of the immune system often also referred to as atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity. It is characterized by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody known as IgE, resulting in an extreme inflammatory response. Common allergic reactions include eczema, hives, hay fever, asthma, food allergies, and reactions to the venom of stinging insects such as wasps and bees.
Mild allergies like hay fever are highly prevalent in the human population and cause symptoms such as allergic conjunctivitis, itchiness, and runny nose. Allergies can play a major role in conditions such as asthma. In some people, severe allergies to environmental or dietary allergens or to medication may result in life-threatening anaphylactic reactions and potentially death.
A variety of tests now exist to diagnose allergic conditions; these include testing the skin for responses to known allergens or analyzing the blood for the presence and levels of allergen-specific IgE. Treatments for allergies include allergen avoidance, use of anti-histamines, steroids or other oral medications, immunotherapy to desensitize the response to allergen, and targeted therapy.
| Allergy roughly refers to an "altered reaction.".The word allergy was first used in 1905 to describe the adverse reactions of children who were given repeated shots of horse serum to fight infection.
Allergy shots are also referred to as allergen immunotherapy . By receiving injections of small amounts of an allergen, your body can gradually develop antibodies and undergo other immune system changes.
Allergy-causing proteins are injected under the person's skin, triggering the body to produce antibodies (protective proteins) which block the pet allergen from causing a reaction. Patients are usually given one dose per week for a few weeks to months (depending on the severity of the allergy) and then can often manage with one injection per month.
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Allergy services may also be delivered by immunologists . A 2003 Royal College of Physicians report presented a case for improvement of what were felt to be inadequate allergy services in the UK. Allergy shots are very safe and many people have great success with them, however, they are very slow to work. It may be six to twelve months before improvement is seen. Allergy shots also are commonly preferred by patients who would rather not use drugs, as the shots are made of an extract of the very things that people are allergic to, e.g. In addition, allergy shots have also been shown to be effective for people with cat allergies, but avoidance is still the best treatment for cat allergies.
An allergy is the body's hypersensitivity to substances in the environment. Allergic reactions range from mild itching, sneezing or eczema (inflamed, itchy skin), to severe hives, hay fever, wheezing, and shortness of breath. An extreme allergic reaction can result in anaphylactic shock, a life-threatening situation in which a person's airway swells shut and blood pressure drops.
Scientists believe allergies originated millions of years ago as a way for the human body to rid itself of parasites and invading worms. The body fights these and other invaders by producing an antibody called immunoglobulin E (IgE for short) in the intestines and lungs. Without modern parasites to fight, IgE reacts to other foreign substances in the body. IgE triggers immune cells to release a number of chemicals, one of which is histamine. Histamine produces hives, watery eyes, sneezing, and itching. The more a person is exposed to allergens, the more the body produces IgE; hence, allergies often get worse with age.
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