Behind the Forecast: Does cold weather affect hair growth

LOUISVILLE, Ky. (WAVE) - It is No-Shave November (also known as Movember), a month where many put down the razors to spark a conversation and raise awareness about cancer and men’s health.

So, does the chilly November air help with hair growth?

Warm air holds much more moisture than cold air. This means that as temperatures drop, the air holds less moisture. The relative humidity is defined by the National Weather Service as a "measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature."

The relative humidity is dependent on the correlation between moisture content and the temperature. It is possible to have 100% humidity at 20 degrees and 80 degrees, but they feel very different. This is why dewpoint is a better indicator of how humid it will feel outside. Dewpoints below 55 degrees typically feel dry and comfortable, while dewpoints over 65 degrees feel incredibly muggy.

Since cold air holds less moisture, that leaves hair drier. Experts recommend using hydrating hair masks during colder months to keep hair healthy. Dry hair is dull hair; the absence of substantial moisture contributes to a lack of shine. Dry hair is also more brittle, according to experts. This causes hair to be more susceptible to split ends. Dry scalps also can contribute to hair loss; dry scalps tend to grow brittle hair that excessive friction (like when we pull hats on and off during the winter) can easily break.

Studies show that cold weather does not lead to hair loss. A lack of humidity and hydration is more often the culprit. A six-year study of 823 women at the University Hospital of Zürich found that they lost the least amount of hair during the winter. It showed that there was a peak in hair shedding in the summer, with a second, less significant, peak during the spring.

Research also shows that the body produces more melatonin in the winter, which helps to regulate the hair growth cycle and thus keeps hair from shedding.

Another study from the University of Bradford studied 14 Caucasian men in Sheffield, U.K., and found that their beard and leg hair grew the least in January and February. Hair growth for these men peaked in the summer months but their hair shed the most during August and September.

Here’s the thing though, hair goes through a cycle of growth and rest. During the anagen, or growth phase, hair follicles produce a hair shaft from root to tip. The anagen phase can last a few years. The regression, or catagen phase, signals the end of growth for your hair. Follicles shrink through the catagen phase, and the hair club is formed; this cycle lasts about 10 days.

Hair’s resting phase, telogen, is when hair can fall out. During the telogen part of the cycle, follicles reset and get ready to start the next growth phase. Each hair goes through the growth cycle at different times. If they didn’t, all our hair would fall out at one time!

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