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Why are allergies becoming more common?


Updated November 20, 2007

Question: Why are allergies becoming more common?
Answer: No one knows for sure. There are various theories why this might be, with the “hygiene hypothesis” representing the most popular reason. The “hygiene hypothesis” refers to the fact that in our clean, modern society, our immune systems no longer have to fight off multiple infections during childhood. The absence of infections results in the immune system shifting away from an “infection fighting” stance towards an “allergies” stance. These two different stances represent opposites as far as our immune system is concerned.

For example, the majority of our children no longer grow up on farms around livestock; they are given multiple immunizations and antibiotics when sick; their environment is “cleaner” than ever, with increased bathing and hand washing. As a result, there is less early exposure to endotoxin, a protein produced by various animals, particularly farm animals, in early childhood. Endotoxin has been shown to shift the immune system away from an allergic response early in childhood. Children who grow up on farms are exposed to large amounts of endotoxin, and therefore have lower rates of allergic diseases.

Does this mean that our children should play in kitty litter boxes and not get vaccinated against childhood diseases? Absolutely not. It probably means that we’re trading potentially life-threatening infections for a shift in our immune systems towards allergies.

Find out ways to potentially prevent the onset of allergies in your children.


Hopp RJ. Genetics and Epidemiology of Allergic Disease. In: Naguwa SM, Gershwin ME, eds. Allergy and Immunology Secrets. 1st ed. Philadelphia: Hanley and Belfus, Inc.;2001:1-11.

DISCLAIMER: The information contained in this site is for educational purposes only, and should not be used as a substitute for personal care by a licensed physician. Please see your physician for diagnosis and treatment of any concerning symptoms or medical condition.

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