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Permanent cures are more elusive. But for more severe allergies, doctors have had some success with a course of treatment that resembles the folk- medicine cure for hangover: patients are immunized with a little hair from the dog that bit them. In this seemingly primitive therapy, allergy shots consisting of allergens taken from such exotic sources as cat saliva, dust- mite droppings and pollen and mold spores are often administered over a few years. Early on, the shots are given as little as six days apart, but as the treatment progresses, the frequency of shots is decreased until it levels off to a monthly pace. Over the same span, the doses are gradually increased until they reach a maintenance level.
In some cases, the treatment pays off. "For pollen," says Dr. Jacquelynne Corey, an allergist at the University of Chicago, "the success rate is great, | around 90%." For dust mites, mold and animal dander, the results are more variable. But why the shots do -- and sometimes don't -- work remains a mystery. Medical researchers know, for instance, that administering the allergens directly into the bloodstream results in the production of immunoglobulin G, rather than IgE, antibodies. Does the presence of IgG block the IgE response? Or does the hair-of-the-dog procedure eventually desensitize key cells in the immune system to the offending allergen? No one knows.
Most doctors are convinced that a faster, more successful cure for allergies is bound to come. Using molecular-biology techniques, researchers have already identified IgE receptors on the mast cell, basically little berths in which the antibody docks. If they can find or synthesize another substance that blocks those receptors, they can prevent IgE from docking and unleashing the mast cell's stream of debilitating chemicals. And as scientists isolate and analyze more and more human genes, they may find the ones that, when defective, cause allergic reactions. Such discoveries could quickly lead to precise tests for allergies and eventually to permanent cures.
Until that time, millions of Americans will continue to sneeze and suffer, victimized by errant genes, pollen grains, mold spores, dust-mite dung and the family cat.