Increases in immune system disasters such as food allergies, asthma cases, hay fever, eczema, lupus, multiple sclerosis and other afflictions have greatly increased in recent years.
Asthma, hay fever, eczema and food allergies are all "allergic diseases" caused by your immune system responding to substances that are ordinarily harmless, such as pollen or peanuts. Autoimmune diseases, which include lupus, multiple sclerosis, Type 1 diabetes and inflammatory bowel disease, also result from your body's defense mechanisms malfunctioning, causing your immune system to attack parts of your body such as your nerves, pancreas or digestive tract.
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 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."
"Overall, there is very little doubt that we have seen significant increases," said Syed Hasan Arshad of the David Hide Asthma and Allergy Centre in England, who focuses on food allergies. "You can call it an epidemic. We're talking about millions of people and huge implications, both for health costs and quality of life."
One reason that many researchers suspect something about modern living is to blame is that the increases show up largely in highly developed countries in Europe, North America and elsewhere, and have only started to rise in other countries as they have become more developed.
Several lines of evidence support the theory. Children raised with pets or older siblings are less likely to develop problems, possibly because they are exposed to more microbes. But perhaps the strongest evidence comes from studies comparing thousands of people who grew up on farms in Europe to those who lived in less rural settings. Those reared on farms were one-tenth as likely to develop diseases such as asthma and hay fever.
Several alternative theories have been presented. Some researchers blame exposure to fine particles in air pollution, which may give the immune system more of a hair trigger, especially in genetically predisposed individuals. Others say obesity and a sedentary lifestyle may play a role. Still others wonder whether eating more processed food or foods processed in different ways, or changes in the balance of certain vitamins that can affect the immune system, such as vitamins C and E and fish oil, are a factor.
"Cleaning up the food we eat has actually changed what we're eating," said Thomas Platts-Mills of the University of Virginia.
Some researchers have begun to try to identify specific genes that may be involved, as well as specific components of bacteria or other pathogens that might be used to train immune systems to respond appropriately.
Washington Post Staff Writer
Tuesday, March 4, 2008