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How do anti histamines work ?

Antihistamines counteract the effects of histamine released by the body when disease-causing microorganisms or antigens such as bacteria, fungi or virus attack it. The body's immune system recognizes its own organs and tissues by the distinctive "self marker" the body cells carry and does not attack it. The system is able to recognize "non-self" molecules, or antigens, and responds by producing antibodies to counteract them. Antibodies are Y-shaped proteins that chemically 'read' surface proteins of every cell they encounter and 'stick' to any that are foreign, thereby marking the antigen for destruction by leukocytes (white blood cells). When the body comes in contact with an antigens, the antibodies release histamine to "kill" the invader. The release of histamine brings more blood and lymph fluid to the site of invasion, which acts to bring more immune cells there to help fight the infection and more blood flow to help carry away poisons. The swelling and fluid caused by blood and lymph vessel swelling results in the symptoms of stuffy nose and watery eyes. What to do? Take an anti-histamine, of course. Even transplanted organs and tissues can cause the body to release histamine. Sometimes innocent and harmless bodies (proteins) such as pollen, peanuts, milk, penicillin etc. may not be recognised by the immune system and provoke it to set off the inappropriate and harmful response known as allergy; in these cases the antigens are known as allergens. Histamine can also cause breathing difficulties by contracting the smooth muscles in the walls of the lungs and blood vessels and cause wheezing. Antihistamine drugs prevent histamine carrying out these actions. They are most often used to treat allergic reactions, although they can also be used to treat other conditions such as migraines, travel sickness, and stomach ulcers. Antihistamines dry up mucus and decrease swelling, but unfortunately, the drying up the normally moist sinuses can make you more susceptible to infection. Antihistamines can also interfere with - and perhaps weaken - the immune system and can lose their efficacy on the body with long-term use. Antihistamine drugs are available as tablets, creams, and injections. The older, first-generation antihistamines tend to cause drowsiness and heart arrhythmias, but the more recent, new antihistamines, cause less drowsiness. Some antihistamines, such as creams for insect bites, and some tablets for hay fever, can be bought over-the-counter from your pharmacist. Despite widespread concern about the risks, most cold remedies available over the counter contain antihistamines. Reading labels or consulting a pharmacist can help people identify cold remedies containing antihistamines. Cold remedies containing antihistamines should not be taken with alcohol, sleep aids, tranquilizers, or other drugs that also cause drowsiness and decrease alertness. Such a combination may intensify the sedating effects of the drugs. Anyone who drives, operates heavy equipment, or performs other activities that require alertness should not take the antihistamines included in OTC products. Children, older people, and people with brain damage may feel nervous, restless, and agitated with pronged use of antihistamines. People with glaucoma, heart disease, or an enlarged prostate gland should consult a doctor before they take any drug that contains an antihistamine. Uma Shankari is a Bangalore-based freelance journalist. She is passionate about writing. She writes regularly on development issues, health and fitness, yoga/meditation, life and relationships. Read some of her articles on Here   Article Source: http://EzineArticles.com/?expert=Uma_Shankari