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Other pervasive allergens are the spores made by molds, both the outdoor kind that grow on crops, grass and dead leaves and the household variety found on foods, leather, furniture and in air conditioners. All these fungi spores can produce vigorous allergic reactions. "Molds are boggling," says Washington University's Lewis. "There can be hundreds of thousands of mold spores per cubic meter of air." And, he points out, a person inhales about 10 or 12 cu m of air each day.
Members of some 2 million U.S. families are allergic to cats. Feline saliva contains the offending substance, a protein called Fel d1 (for Felis domesticus 1) that is left on the fur and skin during preening, a full-time preoccupation of most cats. As a result, houses full of cat hair and dander cause uncomfortable reactions in 25% of allergy sufferers. "Some 70% of cat owners allow their cats to sleep with them in their beds," says Dr. Joseph Wedner, chief of allergy and clinical immunology at Washington University. "There's no better way to make someone allergic to a cat or to make a cat allergy worse than lying there with a cat pressed up against your face." Even the innocent suffer. One example is Dr. Arthur Torre, a Fairfield, N.J., allergist who occasionally treats cat owners. "I'll go in the room with them," he says, "and I'll start wheezing just from the cat dander they have on their person."
At home or away, threats lurk in the form of foods that produce allergic reactions ranging from nausea to death. Shellfish and nuts, especially peanuts, are among the most dangerous to the vulnerable, with the potential of causing anaphylactic shock, which is marked by sudden bronchial spasms, vomiting, plummeting blood pressure and heart arrhythmias. "Peanut allergy is a life-threatening disease," says Dr. John Oppenheimer of Denver's National Jewish Center. "The greatest nightmare for someone with a peanut allergy is dropping dead on a restaurant floor or at a potluck supper or a friend's dinner party."
While shellfish can be avoided, peanuts and peanut products, including some forms of peanut oil, are ubiquitous in foods, showing up unrecognized in such items as chili, stews and meat patties. Canadian businessman Paul Motz has learned to be wary -- and prepared. With seven severe reactions already in his medical dossier, he always carries a vial of the hormone epinephrine (for relaxing bronchial muscles and jump-starting the heart). He also has a supply of cards to hand out to waiters, each bearing the warning "I have an acute allergy to peanuts. Any contact could kill me immediately. Please double-check your recipes." An appropriate tip, to be sure.
Equally lethal to some are insect bites, which cause a fatal allergic reaction in some 40 Americans each year. As many as 20% of people in the U.S. have a severe local response to bites from yellow jackets, hornets, honeybees, wasps and fire ants. An arm swollen to twice its normal size is not unusual. Of the 2 million annually whose reactions to stings spread throughout the body, a few hundred thousand will break out in hives and suffer shortness of breath. Yet, according to the estimate of Dr. Martin Valentine, an allergist at Johns Hopkins, half of those people who would have such dangerous reactions are unaware that they are at risk.