Asthma Questions: The Hygiene Hypothesis

Question: I’ve heard something called the “hygiene hypothesis” being referenced when discussing asthma. What is this?


The “hygiene hypothesis” is a school of thought presented by certain medical studies, discovered during investigations in to why asthma is seemingly on the rise. While by no means a new condition, cases of asthma have been steadily rising since records began. Certain medical studies have tried to find out why this is, and along with environmental factors, the hygiene hypothesis has been suggested for this rise in cases.

“Hygiene hypothesis” is the term used to describe the fact that, as a species, we are far more hygienic than we have ever been. Most households use strong cleaning products, and young children are not as exposed to dirt and bacteria as they were in the 1950s and 1960s. While this cannot really be seen as a bad things, some studies have suggested that it may have contributed to a rise in asthma cases.

Bacteria in the air, when inhaled, is aggravating – and can cause temporary inflammation of the lungs. This usually manifests itself in coughing. Young children in the earlier parts of the 20th century would have had daily exposure to bacteria due to less rigorous hygiene and cleaning standards; as a result, the bronchi of their lungs would appear irritated. The body would then learn how to deal with this, and calm the bronchi down.

Asthma can essentially be described as a irritation of the bronchi. As children nowadays are not exposed to the same levels of bacteria, their bodies do not learn to ‘calm’ the bronchi in their early life. This, some suggest, has lead to a larger number of asthma cases, as when presented with bacteria now, the body is not as well-versed in how to react.