Asthma and the Hygiene Hypothesis: Is Dirty Better?
Updated April 03, 2015.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
Question: Asthma and the Hygiene Hypothesis: Is Dirty Better?
Answer:
You may cringe when your child comes home dirty and smelly after a hard play day -- but the hygiene hypothesis actually proposes that dirty may be better for their health.
Hygiene Hypothesis: What Is It?
The hygiene hypothesis posits that increasing rates of asthma in the Westernized world compared to other places result from our extreme cleanliness. After birth children in non Westernized countries are exposed to greater amounts of germs and develop the associated immune responses.
According to the hygiene hypothesis, children develop asthma and other atopic diseases because their immune systems are not appropriately challenged.
As a result of the lack of exposure, young children's immune systems are not sufficiently stimulated and the immune system actually contributes to the development of asthma, according to the hygiene hypothesis.
Research supporting the hygiene hypothesis points out that children growing up on farms and other rural areas that develop less asthma and allergic disease than kids growing up in cities. What's the difference? Researchers believe children in more rural environments have more exposure to endotoxins, which ultimately decreases overall inflammation and other allergy symptoms.
Hygiene Hypothesis: The Link Between RSV and Asthma
The RSV or respiratory syncytial virus is one of the first viruses children are exposed to. Nearly every child gets exposed and it causes some premature babies great problems. So you might be surprised to know that exposure to this virus actually increases your risk of asthma.
So does this disprove the hygiene hypothesis?
Scientist have been able to determine that exposure to the RSV virus does not stimulate the immune system as do other types of infection, specifically T cells. This lack of stimulation results in an uneducated immune system. How this is exactly related to asthma (e.g. does the RSV virus cause the decreased immune response or is the decreased immune response just an indicator of the immune problem) is not yet known, but currently a topic of great interest to scientists.
Hygiene Hypothesis & RSV- Learn More
RSV Virus Risk Factors, Symptoms, & Prevention
Final Thoughts On The Hygiene Hypothesis
According to the hygiene hypothesis, our sanitized environments lead to less endotoxin exposure and do not allow for young immune systems to appropriately develop. This underdeveloped immune system may then actually contribute to the development of asthma.
While the exact reason for worsening asthma is not known, the next time your muddy, smelly children return from the playground, remember that the activity may be important for their overall health and well-being.
Hygiene Hypothesis -- Learn More
- PBS Hygiene Hypothesis Video (Quicktime)
- PBS Hygiene Hypothesis Video (Real Player)
- Erika von Mutius, a Hygiene Hypothesis Researcher
Hygiene Hypothesis -- More Around About.com
- The Hygiene Hypothesis - Are We Washing Too Much?
- Food Allergies- What is the Hygiene Hypothesis?
- How Does The Hygiene Hypothesis Relate to IBD?
Sources:
American Academy of Allergy Asthma & Immunology. Accessed June 20, 2010. A Little Dirt May Be Good For Your Kids
U.S. Food and Drug Administration. Accessed January 22, 2010. Asthma: The Hygiene Hypothesis