- With Mayo Clinic asthma and allergy specialist
James T C Li, M.D., Ph.D.
read biographyclose windowBiography of
James T C Li, M.D., Ph.D.
James Li, M.D.
"People with allergy or asthma can lead full and healthy lives." — Dr. James Li
Dr. James Li is chair of the Division of Allergic Diseases in the Department of Internal Medicine and a board-certified asthma and allergy specialist. He hopes his expertise and the information on the site educates health care consumers in an area of rapid change both in medications and diagnoses.
"There are a lot of misperceptions about allergy and asthma," says Dr. Li, a New York City native who has been with Mayo since 1985 and works with a group of subspecialists in allergy, asthma and immunology. "I believe it's important to provide truthful, accurate information about allergy and asthma to the public. The more people know, the better they can take care of these conditions."
Dr. Li is a professor of medicine at College of Medicine, Mayo Clinic. He's a past director of the American Academy of Allergy, Asthma & Immunology, the American Board of Allergy and Immunology, and the American Board of Internal Medicine. He's a fellow in the American College of Allergy, Asthma & Immunology.
The American College of Allergy, Asthma & Immunology honored him with the Distinguished Service Award, and the American Academy of Allergy, Asthma & Immunology with its Special Recognition Award.
Risk factors (2)
- Starting solids: When is the right time?
- Infant swimming: Do indoor pools increase asthma risk?
Symptoms (1)
- Wheezing in children: Could it be asthma?
Tests and diagnosis (1)
- Will my child outgrow asthma?
Treatments and drugs (2)
- LABAs for asthma — Should I stop taking them?
- Albuterol side effects: What's normal?
Lifestyle and home remedies (1)
- Asthma triggers: Are hard flooring surfaces better than carpet?
Prevention (1)
- Hygiene hypothesis: Early germ exposure prevents asthma?
Free
E-newsletter
Subscribe to Housecall
Our weekly general interest
e-newsletter keeps you up to date
on a wide variety of health topics.
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
Question
Hygiene hypothesis: Early germ exposure prevents asthma?
Does childhood exposure to germs help prevent asthma?
Answer
from James T C Li, M.D., Ph.D.
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, there are a number of microbes that may cause asthma rather than prevent it, such as respiratory syncytial virus (RSV). For another thing, infections that might help prevent asthma can cause a number of other health problems. The type of germs isn't the only factor that plays a role, either. The severity of an infection — and when it 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 general, exposure to germs is likely to do more harm than good. Help your child avoid contacting or spreading germs with steps such as thorough hand washing, avoiding touching the eyes, nose or mouth, and covering the nose and mouth with a tissue when coughing or sneezing.
Next questionStarting solids: When is the right time?
- Tang EA, et al. The hygiene hypothesis. In: Adkinson M, et al. Middleton's Allergy: Principles and Practice. 7th ed. Philadelphia, Pa.: Mosby; 2008. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-0-323-05659-5..00043-7--cesec2&displayedEid=4-u1.0-B978-0-323-05659-5..00043-7--cesec3&uniq=216050134&isbn=978-0-323-05659-5&sid=1043216341#lpState=closed&lpTab=contentsTab&content=4-u1.0-B978-0-323-05659-5..00043-7--cesec2%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-0-323-05659-5. Accessed Aug. 20, 2010.
- Lang DM, et al. The hygiene hypothesis, airway hyperresponsiveness, and disease progression. In: Carey WD, et al. Cleveland Clinic: Current Clinical Medicine. 2nd ed. Philadelphia, Pa.: Saunders Elsevier; 2010. http://www.mdconsult.com/book/player/book.do?method=display&type=bookPage&decorator=header&eid=4-u1.0-B978-1-4160-6643-9..00001-1--s0030&uniq=216050134&isbn=978-1-4160-6643-9&sid=1043219820#lpState=closed&lpTab=contentsTab&content=4-u1.0-B978-1-4160-6643-9..00001-1--s0030%3Bfrom%3Dtoc%3Btype%3DbookPage%3Bisbn%3D978-1-4160-6643-9. Accessed Aug. 20, 2010.
- 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.
Find Mayo Clinic on