The Hygiene Hypothesis and Rising Rates of Asthma

Many years ago, I came across a tale of The Wheezing Wolf and the Three Little Pigs (you could call it a breathless spin on a timeless children’s classic). It is also a tale that manages to very creatively highlight a disease state which affects a large number of children worldwide – that’s right, asthma! It is estimated more than 22 million people (~6 million children) in the United States have some form of asthma, a chronic but reversible condition which causes inflammation and bronchoconstriction of our airways1.

Although there is no magic bullet or cure for people who suffer from asthma, we have a large variety of medications that allow for proper management which helps prevent long term airway remodeling, permanent lung damage, hospital stays and emergency room visits1. You might be wondering what causes people to acquire asthma… maybe it’s people spending a lot of time with wolves who huff and puff or maybe it just happens to be all the Hufflepuffs? Well, data is gathered meticulously to better highlight trends in asthma for this very reason. For example, one trend already identified makes clear that african american and hispanic children are generally more likely to experience mortality from asthma related causes1. Below you will find several interactable modules which outline the rise in asthma cases over the years but also the demographic aggregation of cases across the United States:

One theory that has gained traction over the years to explain the rising cases of asthma is called the hygiene hypothesis. This hypothesis suggests our post natal immune response is compromised by an ultra clean environment, causing a lack of exposure to infectious organisms and consequently leading to an “uneducated” immune system (which is more likely to predispose a child in developing conditions like asthma)3. The bacterial protein lipopolysaccharide (LPS) is an example of how our immune system can grow, learn and graduate school by “switching” on toll-like receptor 4 (TLR4), a characteristic shared by the respiratory syncytial virus (RSV) F protein commonly encountered by infants3. It is still up in the air whether RSV is helpful in the same way LPS is in regards to building a solid immune system, or whether it actually does more harm than good by potentially suppressing proliferation of T cells; however, it is an area of expanding research as we continue to ponder what effects clean houses could potentially have on the rising incidence of disorders such as asthma3. If you would like to learn more about the hygiene hypothesis and the potential implications as we navigate through the COVID-19 pandemic, this article (“The hygiene hypothesis, the COVID pandemic, and consequences for the human microbiome”) is a nice read.

As a whole, asthma attacks can vary in severity and in nature from one person to another; however, common triggers include tobacco smoke, dust mites, pollen, air pollution, mold, a man’s best friend, perfumes, harsh cleaners/disinfectants and even acid reflux2. It is important for patients who suffer from asthma to identify and avoid triggers. For example, encouraging tobacco cessation in households with smokers or using an air cleaner with a HEPA filter for people who may be allergic to their furry friends2. And lastly, if there is one thing we know from the hygiene hypothesis, it’s that people love to clean their homes. It is especially true now perhaps more than ever before and we may very well see an even steeper rate of asthma cases moving forward, even if just from COVID sequelae alone. Here is a CDC guide to properly cleaning and disinfecting homes that patients (especially those sensitive to harsh detergents or cleaners) may find useful; it’s even COVID approved. 


Jean Hanna


  1. Asthma Fact Sheet. (2019, May 22). Retrieved from
  2. Common Asthma Triggers. (2020, August 21). Retrieved from
  3. Asthma: The Hygiene Hypothesis. (2018, March 23). Retrieved from

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