Can Cleanliness Increase the Risk of Allergies and Asthma?

Jacqueline Britz, Cancer Prevention and Treatment Fund

Why have allergies and asthma risen so dramatically in recent years?  From 1980 to 1994, asthma rates in the United States increased 75% overall, with rates increasing among individuals of all races, all age groups, and both sexes.  An especially disturbing increase in allergies, approximately 160%, was found for children under five.[1] About 70% of individuals with asthma also have allergies.[2] These statistics are very troubling, especially as asthma results in about 217,000 emergency room visits each year.[3]

Research indicates that some of the products we use to avoid germs, such as antibacterial soaps, hand sanitizers, and laundry detergents, may contribute to the development of conditions like asthma and allergies.  According to the FDA, the hygiene hypothesis “suggests that the critical post-natal period of immune response is derailed by the extremely clean household environments often found in the developed world.”[4] In other words, an environment that is “too clean” including the current Western diet, may not allow enough exposure for germs to adequately “educate” the developing immune system of a young child.  The resulting “inadequate” defenses can play a part in the development of asthma or allergies.

A recent study may shed light on the hygiene hypothesis and how chemicals may influence immune function.

Impact of Environmental Toxicants on Allergies and Immune Function

According to a new study by Dr. Erin Rees Clayton and her colleagues at the University of Michigan School of Public Health, young people with overexposure to antibacterial soaps containing triclosan may be at greater risk for suffering from allergies.[5] Further, overexposure to Bisphenol A (BPA) may weaken the immune system of adults.

Both of these chemicals belong to a class of toxicants known as endocrine-disrupting compounds.  Often found in personal care and other consumer products, food, pharmaceuticals, and the environment, these compounds mimic or disrupt hormones.  What is particularly troubling about BPA and triclosan is that they are in many products that children and adults are exposed to regularly.  Triclosan is contained in antibacterial soaps, diaper bags, laundry detergents, toothpaste, pens, children’s toys, and medical devices.  Many plastics, including those that line food and soft drink cans, contain BPA, in addition to other products, like dental sealants.

While previous studies have researched the influence of BPA and triclosan on animals’ immune function, the Rees Clayton study was the first to investigate this relationship in humans. The study used data from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) and looked at the relationship between urinary levels of BPA and triclosan and markers of how well the immune system functioned. The markers used were the diagnoses of allergies or hayfever, and overall levels of a particular antibody in the blood called cytomegalovirus antibody.

The study included two age groups: participants over the age of 18 and participants between 6 and 18. Participants in the younger age group that had higher levels of triclosan were more likely to have been diagnosed with hayfever or allergies, which seems to support the hygiene hypothesis.  While this same relationship was not seen with BPA, high levels of BPA exposure were associated with high antibody levels for those over age 18 (a sign of improper functioning of an immune response called the cell-mediated immune system).

The findings are interesting, but more research is needed to understand the link between allergies, hayfever, and triclosan.

Flu Infection may help Prevent Asthma

With a similar interest in germs and asthma, Dr. Ya-Jen Chang and her colleagues, published in the Journal of Clinical Investigation, studied how the flu virus may later help prevent asthma.[6] In this study, active infectious flu agents were found to give mice protection against asthma only if the mice were exposed when they were young (2 weeks old). If the mice were exposed to flu when they were older, the exposure did not provide any protection against asthma. Researchers emphasized that this “influenza-induced protection” does not mean that we should expose people to dangerous infections in an effort to prevent asthma, but instead how this information may be helpful in the development of a new therapeutic strategy for treating asthma. One of the authors, Dale Umetsu, MD, PhD, a Professor of Pediatrics at Harvard Medical School, explains “If we can understand how infections prevent asthma, we may be able to replicate the good parts and avoid the bad parts of infection and develop new treatments for children to prevent asthma.”

To be Clean or Not to be Clean…

These research results don’t mean that exposure to germs is always good. Germs spread disease, and regular hand-washing and other good hygiene habits will help prevent the spread of those germs. Nonetheless, the data suggest that using too many antibacterials may contribute to asthma and allergies, and that it can be beneficial to avoid over-exposure to products containing BPA and triclosan. There are many greener triclosan-free products, including sanitizers and disinfectants like Burt’s Bees Aloe & Witch Hazel Hand Sanitizer, CleanWell, For My Kids, and Clean George. Some companies that provide canned food with BPA-free cans include Eden Foods and Vital Choice. While it is not realistic to avoid exposure to all chemicals, mindful consumers can reduce exposure to those thought to be particularly harmful.


  1. Centers for Disease Control. Surveillance for Asthma – United States, 1960-1995, MMWR, 1998; 47 (SS-1).
  2. World Health Organization. Global surveillance, prevention and control of chronic respiratory diseases: a comprehensive approach, 2007.
  3. Pitts SR, Niska RW, Xu J, Burt CW. National Hospital Ambulatory Medical Care Survey: 2006 emergency department summary. National health statistics reports; no 7. Hyattsville, MD: National Center for Health Statistics. 2008.
  4. Asthma: The Hygiene Hypothesis. What do clean houses have in common with childhood infections? (2009, June 18). Retrieved from U.S. Food and Drug Administration website:
  5. Rees Clayton, E. M., Todd, M., Dowd, J. B., & Aiello, A. E. (2010, November 29). The Impact of Bisphenol A and Triclosan on Immune Parameters in the US Population, NHANES 2003-2006. Environmental Health Perspectives.
  6. Chang, Y.-J., et al. (2011, January 4). Influenza infection in suckling mice expands an NKT cell subset that protects against airway hyperreactivity. Journal of Clinical Investigation, 121(1), 57-69. doi:10.1172/JCI44845