By Rob Stein
Washington Post Staff Writer
Tuesday, March 4, 2008; A01
First, asthma cases shot up, along with hay fever and other common allergic reactions, such as eczema. Then, pediatricians started seeing more children with food allergies. Now, experts are increasingly convinced that a suspected jump in lupus, multiple sclerosis and other afflictions caused by misfiring immune systems is real.
Though the data are stronger for some diseases than others, and part of the increase may reflect better diagnoses, experts estimate that many allergies and immune-system diseases have doubled, tripled or even quadrupled in the last few decades, depending on the ailment and country. Some studies now indicate that more than half of the U.S. population has at least one allergy.
The cause remains the focus of intense debate and study, but some researchers suspect the concurrent trends all may have a common explanation rooted in aspects of modern living -- including the "hygiene hypothesis" that blames growing up in increasingly sterile homes, changes in diet, air pollution, and possibly even obesity and increasingly sedentary lifestyles.
"We have dramatically changed our lives in the last 50 years," said Fernando Martinez, who studies allergies at the University of Arizona. "We are exposed to more products. We have people with different backgrounds being exposed to different environments. We have made our lives more antiseptic, especially early in life. Our immune systems may grow differently as a result. And we may be paying a price for that."
Along with a flurry of research to confirm and explain the trends, scientists have also begun testing possible remedies. Some are feeding high-risk children gradually larger amounts of allergy-inducing foods, hoping to train the immune system not to overreact. Others are testing benign bacteria or parts of bacteria. Still others have patients with MS, colitis and related ailments swallow harmless parasitic worms to try to calm their bodies' misdirected defenses.