DOWN and DIRTY
Did having a nice, clean childhood give you hay fever?
A LLERGIES ARE BECOMING SO COMMON YOU’D THINK THEY WERE CONTAGIOUS. They’re almost fashionable. I know people who attribute every sniffle or mood swing to an allergy, in the same way that every heat wave, fogbank, or thunderclap gets blamed on global warming.
You may have noticed that Lewis and Clark didn’t complain that the great outdoors gave them hay fever. That’s because the ailment was so rare it hadn’t yet been described in medical literature. ONLY IN 1819 DID A DOCTOR DESCRIBE AN ILLNESS IN WHICH THE EYES GET ITCHY AND THE NOSE RUNNY.
Respiratory allergies and asthma (a closely related disease) seem to have been on the rise ever since. Some scientists have offered an intriguing, if unproved, explanation: the hygiene hypothesis. Basically, our lives aren’t dirty enough.
To fight invaders, our immune system uses a battalion of cells, notably two commandos called Th 1 and Th 2. An allergy or asthma sufferer’s Th 2 cells are out of control, waging total war against harmless substances. When such a persons Th2 cells encounter one of the millions of pollen grains churned out by the average ragweed plant, they trigger the production of immui1oglobulin F - a weapon designed to fight disease, not pollen—inflaming the respiratory passages in the process.
What made the human immune response misfire after a few million years of working just fine? Our modern, man made environment may hold the answer.
“WHAT’S THE MAJOR HEALTH CHANGE OF THE PAST 200 YEARS?
This could explain some provocative findings. Respiratory allergies seem to be less prevalent in poor societies than in rich ones. People raised on farms have lower rates of allergies than those raised in cities. Children who attended day care have lower allergy rates.
What’s going on at the cellular level? No one’s sure, but the key may be the balance of power between our Tb I and Th2 defenses. Perhaps our immune systems need to be calibrated in childhood, “learning” to produce Tb I when assaulted by diseases like hepatitis A and tuberculosis. Now that these illnesses are much scarcer, at least in some parts of the world, many of us may not produce enough Tb I to help control that rampaging Th2.
So maybe we’re cave people trapped in a world of antibacterial hand wash . Still, compared with the diseases our ancestors suffered, notes Prussin, “it may not be so bad to have an itchy nose.
Washington Post Staff Writer
EVERY BAD REACTION—TO A PLANT, A PET, OR A PILL— ISN’T AN ALLERGY. Consider penicillin. Ten out of every hundred patients in U.S. hospitals report that they’re ‘allergic” to penicillin, but at least six of those are almost certainly wrong . Side effects common to antibiotics—like diarrhea and stomachache—don’t mean you’re allergic. Genuine penicillin allergy is an immune system blowup: Reactions vary from merely miserable (hives) to life threatening (constricted airways and tumbling blood pressure) . It matters that you know if you’re truly allergic because penicillin remains the first-choice treatment for infections from strep throat to syphilis. Rule it out and you may have to settle for a less effective, more expensive drug with a longer list of potentially nasty side effects.
Welcome to Who Knew?
—a new science column by Joel Achenbach.
This month (September 2002) there’s more on allergies at: nationalgeographic.com/ngm/resources/0209
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