An allergy is a by the body’s immune system against a normally harmless substance, or allergen. Almost anything can trigger an allergic reaction addition to those pictured to the ri ht, some common allergens are molds, tobacco smoke, certain foods ad food additives, insect venom, and chemicals in plants, cosmetics, perfumes, detergents, and soaps. The first time a allergen enters the body, the immune system reacts by making a defensive antibody called IgE. This initial exposure does not produce symptoms, but the IgE a triodes become attach to other defending parts of the immune ne system, either basophilic, types of white blood cells, or mast cells,which line he airways, intestines, and skin. On a future exposure to the allergen, the programmed antibodies bind to it and signal the mast cells or basophils to produce a barrage of histamines an other substances that cause allergi symptoms. Because histamines exert the greatest effect on the s in mucous membranes, eyes, lungs, and gastrointestinal tract, most allergic reactions involve these organs. Depending on the nature of the allergy, symptom range on the sneezing, runny nose, an itchy, teary eyes of hay fever r, to hives, headaches, diarrhea, and he life threatening systemic collapse of anaphylactic shock. Doctors do not fully understand why so many people develop allergies. But because they run in families, an inherited predisposition is likely.
Diagnostic Studies an Procedures
In most cases, symptoms of an allergic reaction are self evident, but finding just what triggers them often requires considerable detective work. Doctors start by asking a number of questions such as: Are the symptoms seasonal? Do other family members have similar symptoms? What seems to trigger them? Do you own any pets? A physical examination helps to rule out other conditions that have similar symptoms. Allergy tests may then be ordered to pinpoint specific allergens. The most common are skin tests, in which the skin is exposed to small amounts of suspected allergens and then observed for a reaction. Alternative studies include provocation tests, in which the patient inhales or ingests suspected allergens, and blood tests to look for IgE antibodies. Exposure to allergens should always be done in a doctor’s office or clinic, so that if a severe reaction should occur, it can be treated immediately.
Medical Treatments
Doctors agree that the best approach is to identify and then avoid the suspected allergen. Unfortunately, avoidance is not always possible. In such cases, treatments vary according to severity of symptoms and the types of allergens.
Allergy Medications
Hay fever and other types of pollen allergies are usually treated with drugs that counteract or inhibit histamines. The antihistamines in many nonprescription allergy medications produce drowsiness. (Such antihistamines should never be taken with alcohol, which increases their sedative effect. Also, they may worsen glaucoma, as well as prostate and urinary tract disorders.) There are prescription antihistamines, which do not enter the brain and are nonsedating; examples include terfenadine (Seldane) and astemizole (Hismanal). An alternative prescription medication, chromolyn sodium (Nasalcrom), is an aerosol nasal spray that inhibits the mast cells from releasing histamine, thus preventing nasal congestion. In severe cases, steroids may also be prescribed. These work by temporarily blocking the action of white blood cells. They also block prostaglandins, body chemicals that produce inflammation and swelling. Steroids that are used for treating allergies are usually inhaled or applied to the skin. Other allergy medications work by countering specific symptoms. For example, decongestants relieve nasal stuffiness by constricting the tiny blood vessels in the nose. Topical medications and sprays help to alleviate itching, inflammation, and other skin reactions. Some types, such as calamine, work by soothing and lubricating the surface of the skin; others,such as benzocaine, are local anesthetics that numb the skin.