Children growing up in rural areas, around animals and in larger families seem to develop asthma less often than do other children. According to the hygiene hypothesis, this is due to increased exposure to particular viruses, bacteria or parasites.
The hygiene hypothesis proposes that childhood exposure to germs and certain infections helps the immune system develop. This teaches the body to differentiate harmless substances from the harmful substances that trigger asthma. In theory, exposure to certain germs teaches the immune system not to overreact.
But preventing asthma isn't as simple as avoiding antibacterial soap, having a big family or spending time on the farm. For one thing, a number of microbes — such as respiratory syncytial virus (RSV) — may cause asthma rather than prevent it. In addition, infections that might help prevent asthma can cause a number of other health problems. The type of germ isn't the only factor that plays a role, either. The severity of an infection and when the infection occurs during childhood also appear to matter.
More research is needed to understand exactly how childhood germ exposure might help prevent asthma. What we do know is that in children with asthma, exposure to germs is likely to do more harm than good.
June 02, 2017
- O'Hehir RE, et al. Asthma. In: Middleton's Allergy Essentials. Edinburgh, U.K.: Elsevier; 2017. http://www.clinicalkey.com. Accessed March 24, 2017.
- Bennett JE, et al., eds. Mucosal immunity. In: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2015. http://www.clinicalkey.com. Accessed March 24, 2017.
- Holt PG, et al. 99th Dahlem Conference on Infection, Inflammation and Chronic Inflammatory Disorders: The role of infections in allergy — Atopic asthma as a paradigm. Clinical and Experimental Immunology. 2010;160:22.
- Weber J, et al. Asthma and the hygiene hypothesis: Does cleanliness matter? American Journal of Respiratory and Critical Care Medicine. 2015;191:522.
- Platts-Mills TAE, et al. Increasing prevalence of asthma and allergic rhinitis and the role of environmental factors. http://www.uptodate.com/home. Accessed March 24, 2017.
- Bloomfield SF, et al. Time to abandon the hygiene hypothesis: New perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene. Perspectives in Public Health. 2016;136:213.