According to research released in 2019, there might be a link between hair loss and air pollution, more specifically, dust and diesel particulate matter (PM). After exposing human follicle dermal papilla cells (HFDPCs) to these air pollutants, the study’s authors assessed protein levels in hair follicles responsible for hair growth (β-catenin).
As lead author Hyuk Chul Kwon told Allure, “The research found that when the cells on the human scalp were exposed to common air pollutants created from burning fossil fuels, the proteins in the cells that are responsible for hair growth and hair retention were significantly reduced.” So if you live in a large city that has a lot of the common air pollutants, it might be having an unexpectedly damaging effect on your hair. Lifestyle changes associated with living in large cities, such as a nutritionally deficient diet, may also contribute toward hair loss, per Dr. Divya Sharma, a trichologist in Bengaluru (via The Economic Times).
Stress brought on by living a fast-paced lifestyle can also be one of the reasons you could be losing your hair. According to a 2021 study on mice published in Nature, there is a link between chronic stress and hair loss. Interestingly, the researchers found an acceleration of the hair growth phase when the stress hormone was removed (via The Harvard Gazette).
But if hot weather can make you shed more, where did the notion that “summer makes your hair grow longer” come from?