Ask any doctor for the most important medical advances of the past century and among the answers will be public health victories such as indoor plumbing and improved sanitation. We've all enlisted in the war against germs, brandishing disinfectant sprays and antibacterial soaps. But some specialists are beginning to think that our squeaky-clean lifestyle may be breeding an alarming increase in the number of children with allergies.
"It may be that exposure to bacteria and other infectious agents early in life is a good thing," suggests Robert A. Wood, M.D., an associate professor of pediatrics at the Johns Hopkins University School of Medicine in Baltimore. "It's possible that it focuses your immune system on fighting microbes and directs it away from mounting allergic attacks against harmless pollens and other environmental debris."
This theory, known among scientists as the Hygiene Hypothesis, is revolutionizing the world of allergy research. It may explain why respiratory allergies are nearing epidemic levels in developed countries. And it has inspired innovative research that has the potential to produce a new approach to treatment.
As many as 40% of children in the U.S. have allergic rhinitis, the condition that brings on nasal congestion, sneezing, and a runny, itchy nose. Some kids suffer seasonally from spring-to-fall plant pollens. Even more are affected year-round by indoor dust mites, mold spores, animal dander, and cockroach allergens. Each year, allergy symptoms and complications cause children to miss 2 million days of school, according to a recent task-force report by leading allergy organizations. Many children with allergies go on to develop asthma, an inflammation of the lungs that causes breathing difficulties.