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The Hygiene Hypothesis: Can We Be Too Clean? (page 3)

By — American Academy of Allergy, Asthma, & Immunology
Updated on Mar 10, 2009

It’s hard to answer that question. There are good and bad bugs. RSV and Rhinovirus (viruses causing the common cold and respiratory infections), for example, are known to increase the risk for development of asthma in the future. However, exposure to hepatitis virus and intestinal parasites – which are serious health threats - were shown to prevent development of allergies.

It probably is not wise to expose children to dangerous pathogens for prevention of allergies, but in my opinion, the evidence supporting a hygiene hypothesis does suggest that we could probably allow ourselves to be a little more relaxed about hygiene. This would include not using antibacterial soaps all the time, and not wiping our children’s hands constantly with disinfecting wipes—since the use of antibacterial cleaning products has also been associated with higher incidence of asthma.

Antibiotics wipe out bugs. By the hygiene hypothesis, does that increase risk of allergies?
The use of antibiotics in the first year of life has been linked to asthma and other allergic diseases. When antibiotics are needed for treatment of an infection caused by bacteria their benefit will outweigh the risk of developing allergies. However, antibiotics should not be overused.
Are pets in the home good or bad?

Studies seem to show that living with pets early in life may actually protective for development of allergies. Dogs seem to be better for allergy prevention than cats. Of course the best preventative outcomes were observed in children who grew up on farms with exposure to cattle and other barn animals. Several researchers concluded that organisms in cattle dust and manure may be the stimuli that their immune systems needed to prevent asthma.

The hygiene hypothesis can only account partly for the increase in allergies. There is also a genetic component which influences why certain people will develop allergies, but others will not despite living under the same circumstances. An approach to examine the allergy epidemic from different angles, epidemiologic and genetic, is only recently starting and produces fascinating results on the effect particular gene-environment interactions might have in the development of allergy. The most important point is that thousands and millions of separate risk factors act in concordance in the development of allergies.

 

Corinna S. Bowser, MD, is an allergist/immunologist based in Havertown, Pennsylvania.

The American Academy of Allergy, Asthma & Immunology is the largest professional medical association devoted to the research and treatment of allergic disease. The AAAAI offers educational materials for patients online at www.aaaai.org.

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