Hygiene Hypothesis Revisited

This is the latest wrinkle in the hygiene hypothesis—the notion that exposure to bacteria trains the infant immune system to attack bad bugs and ignore harmless things like pollen and cat dander. But what's interesting about this study is that it gets specific; not just any old germs or allergens will do. Inner-city children who were exposed to cockroach, mouse and cat allergens in the first year of life had less wheezing at age 3. And children exposed to a wider variety of bacteria, especially those in the Bacteriodes and Firmicutes groups, were less likely to develop allergies or asthma. Children exposed to both did best of all, reports Nancy Shute. (2) It adds a degree of precision to the broad concept of the hygiene hypothesis, although a strange quote is attributed to one of the study's co-authors. “What we found was somewhat surprising and somewhat contradictory to our original predictions,” said Dr. Robert Wood, chief of the Division of Allergy and Immunology at the Johns Hopkins Children's Center in Baltimore. “It turned out to be completely opposite—the more of those three allergens you were exposed to, the less likely you were to go on to have wheezing or allergy. (3)

Steve Milloy observes, “The hygiene theory of asthma has been around for many years. Yet an allergist at Johns Hopkins is 'stunned' to find out this basic immunological phenomenon? Desensitization is the bedrock of allergist treatment and he didn't know that?” (4) The hygiene hypothesis was first voiced by a British epidemiologist, D. P. Strachan in 1989. The hypothesis is that our immune system needs a certain amount of bacteria on which to flex its muscles. Deprived of it, the white cells that are designed to fight bacteria fail to develop, and the other white cells—those designed to make antibodies to defend the body against microbial dangers as well as to produce allergic reactions—will take over. (5) Some examples:

• Prior research has shown that children who grow up on farms have lower allergy and asthma rates, possibly due to their regular exposure to bacteria and microbes. (1)
• Diary farmers are as much as five times less likely to develop lung cancer. (6)
• The youngest children in large families face a smaller chance of getting asthma because their older siblings have passed many infections on to them. (7)
• An Italian study showed that men heavily exposed to microbes were less likely to experience respiratory allergy. (7)
• Several other studies have shown that exposure to measles, parasites, and tuberculosis seems to reduce the risk of getting asthma. (7)

For years the increase in asthma has been associated with increasing air pollution. However, asthma is increasing in incidence yet air pollution is declining dramatically. The EPA is now claiming that carbon dioxide causes asthma. In an effort to win public support for the EPA's recently proposed regulations to reduce carbon dioxide emissions from coal burning power plants an estimated 30 percent by 2030, the White House has begun a campaign in which it claims the carbon dioxide 'pollution' causes children to get asthma. (8) Someone should show them this latest report. Perhaps the EPA should regulate cockroach, mouse and cat allergens. Jack Dini Livermore, CA References 1. Susan V. Lynch et al., “Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children,” Journal of Allergy and Clinical Immunology, June 2014 2. Nancy Shute, “Early exposure to bacteria protects children from asthma and allergies,” npr.org, June 6, 2014 3. Dennis Thompson, “Too-clean homes may encourage child allergies, Asthma: study,” consumer.healthday.com, June 6, 2014 4. Steve Milloy, “Johns Hopkins proves up the hygiene theory of asthma? Big surprise?”, junkscience.com, June 9, 2014 5. Katherine Ashenburg, The Dirt On Clean: An Unsanitized History, (New York, North Point Press, 2007), 290 6. Jessica Marshall, 'Filthy healthy,” New Scientist, 197, 34, January 12, 2008 7. Bjorn Lomborg, The Skeptical Environmentalist, (New York, Cambridge University Press, 2001), 187 8. Jerome R. Corsi, “Global warming threat? Now it's asthma,” mobile.wnd.com, June 11, 2014