William Penn Life, 2004 (39. évfolyam, 1-12. szám)
2004-06-01 / 6. szám
Imssaaamaesssi Seasonal / Allergies How to tell if you have an allergy and what you can do about it by Harrison Wein, Ph.D. from Word on Health, a publication of the National Institutes of Health Sometimes it's hard to know whether you're suffering from allergies or a string of colds. Their symptoms--like sneezing, coughing and a runny nose—are similar. If you have these symptoms every spring or fall, or all through the growing season, it's a good bet you've got seasonal allergies, or hay fever. Doctors call this type of allergy "seasonal allergic rhinitis". Whatever its name, it can make you absolutely miserable. Allergic rhinitis may not seem dangerous in itself, but it can play a role in other diseases like asthma, a chronic and potentially fatal lung disease, and sinusitis, an infection in the hollow air spaces of the skull surrounding the nose. There is no cure for allergy, but there are ways to control its symptoms and, hopefully, to prevent it from triggering more serious conditions like asthma and sinusitis. The Allergic Response Whether allergic rhinitis strikes by season or lasts all year long, it is essentially the same disease. Seasonal allergic rhinitis is frequently caused by pollen released into the air by trees, grasses and weeds as part of their reproductive cycle. Molds can cause similar allergic symptoms. They release tiny spores that ride on the wind to establish the mold in new places. Whether pollens or spores, when these airborne allergens (the name for allergy-causing compounds) get into your nose and your eyes, they can cause allergies. But what exactly is an allergy? Everybody is exposed to these pollens and spores, but only some develop allergies to them. An allergy comes about when the immune system, which is there to protect us from microbial invaders like viruses and bacteria, reacts to a normally harmless substance. Specialized cells of the immune system-known as B cellsmanufacture molecules called antibodies to bind very specifically to different foreign invaders. There are five different classes of antibodies, each with its own function. One of these classes of antibodies, IgE, causes the symptoms of allergies. Scientists aren't actually sure what protective role IgE antibodies normally have. "The speculation is that IgE may be involved in host defenses against parasites," says Dr. Dean Metcalfe, Chief of the Laboratory of Allergic Diseases at the National Institute of Allergy and Infectious Diseases. But since most clinical trials are conducted where there are few diseases caused by parasites, it's been difficult to test this theory. What scientists do know is that IgE antibodies attach to the surfaces of two types of immune system cells: mast cells and basophils. When these IgE encounter the allergen they were manufactured to recognize-for example, on a pollen grain or a mold spore—they attach like a key in a lock and trigger the mast cells and basophils to release the little packets of chemicals they contain. Those chemicals include histamine and other compounds that cause local inflammation, leading to the symptoms that you know as an allergy: sneezing, coughing, a runny or clogged nose, postnasal drip, and itchy eyes and throat. When cells make IgE to some environmental antigen that most people don't respond to, the mast cells and basophils are activated when you don't want them to be, and you have an allergy. Scientists think that some people simply have a genetic tendency to develop allergies. "The genes themselves have not yet been identified," Dr. Marshall Plaut, Chief of NIAID's Allergic Mechanisms Section, says. "But there's an impressive amount of work that's been done to identify regions in chromosomes where there appear to be genes associated with allergy." Recognizing an Allergy Sometimes it's obvious you have allergic rhinitis. If you have symptoms like a runny nose and itchy eyes all year round, it's a good bet your condition is caused by allergies. The culprit may be something indoors like dust mites in your bedding or carpet, or mold in the shower. Many allergies are more acute and 6 William Pen lile, June 2004
