Q. A friend recently told me kids are more prone to developing asthma and allergies when they are not exposed to germs, such as dirt and pets. Is this true?
A. Yes, if you believe researcher D.P. Strachan’s “hygiene hypothesis,” first published in the British Medical Journal in 1989.
According to Strachan, we are born with an immature immune system that needs to be stimulated and ‘trained’ to develop normally. When our immune system is exposed to viruses and certain bacteria during early life, TH1 lymphocytes could be stimulated, leading to the development of a non-allergic normal immune system.
In a sterile environment, the immune system overreacts to food, environmental stimuli and viruses, which results in TH2 stimulation and the development of asthma and allergic diseases. Limiting exposure to bacterial and infectious diseases increases the risk of developing asthma and allergic diseases.
Community studies have shown that allergic diseases are more prevalent in industrialized countries compared to ones that are more rural. The National Heart, Lung and Blood Institute estimates that asthma is 1.75 times greater in prevalence today than in 1980. National data indicates that the number of children with asthma has doubled in the past 15 years.
Children raised in rural environments, especially with farm animals, have a lower incidence of allergies. Children enrolled in day care early in life, those raised with multiple siblings, and children growing up with pets have a lower incidence of allergies and asthma.
Although there is much support for the hygiene hypothesis, it doesn’t satisfactorily answer the question of why there are more asthma deaths in some of the nation’s inner cities, where the environment is not “clean”.
Susan Raschal, D.O.
Covenant Allergy & Asthma Care
1350 Mackey Branch Drive, Ste. 114
Chattanooga, TN 37421
Ph. (423) 468-3267