Wh0 kNeW ..

 WHO KNEW?

ALLERGIES

DOWN AND DIRTY

DID HAVING A NICE,CLEAN CHILDHOOD GIVE YOU HAY FEVER ?
Allergies 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.Thats 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 seem to have been on the rise ever since.Some scientists have offered an in triguing,if unproved,explanation: the hygiene hypothesis. Basicallly,our lives aren’t dirty enough.

To fight invanders,our immune system uses a battalion of cells,notably two commandos called Th1 and Th2.An allergy or asthma sufferer’s Th2 cells are out of control,waging total war against harmless substances.When such a person’s Th2 cells encounter one of the millions of pollen grains churned out by the average ragweed plant,they trigger the production of immunoglobulin E-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? It’s basically hygiene,”says Calman Prussin,a researcher with the National Institute of Allergy and Infectious Diseases.For many people the days of unsanitary,crowded environment-and the bacteria,viruses,and parasites that come with them-have passed.
This could explain some provocation 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.

Whats going on at the cellular level?No one’s sure,but the key may be the balance of power  between our Th1 and Th2 defences.Perhaps our immune system need to be calibrated in childhood,”learning” to produc Th1 when assaulted by diseases like hepatitis A and tuberculosis.Now that this illnesses are scarcer,at least in some part of the world,many of us may not produce enough Th1 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.”