If you’ve been staring at your brush or your shower drain and feeling like you’ve been losing a lot of hair lately, don’t freak out. A new British Journal of Dermatology study suggests that shedding more strands in the summer and fall is totally normal.
A seasonal pattern of hair loss has been long suspected; it’s been observed anecdotally and documented in previous small studies. But those studies have focused on just one demographic or geographic location, so it hasn't been possible to know if those findings apply to everyone.
Researchers at Johns Hopkins and Washington University changed that by compiling Google Trends data from eight countries in four hemispheres with high search rates for the term “hair loss." They looked at search volume from 2004 through 2016, and compared the data month to month and season to season.
Across all eight countries, the results were the same: People searched the Internet using phrases related to hair loss more frequently in the summer and fall compared to the winter and spring. The finding is relevant to doctors whose patients complain of hair loss in those two seasons, the authors say, and it may be useful in assessing how effective certain therapies are at treating the condition. But more research is needed, they add, to determine exactly why this pattern happens—and how much patients should care.
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“Mildly increased hair loss in the summer and fall is normal,” co-author Shawn Kwatra, MD, assistant professor of dermatology at Johns Hopkins University School of Medicine, tells Health. “This is speculative, but from an evolutionary perspective one of the roles of hair loss is to provide warmth,” he says. “This would be less necessary during the summer months.”
The tendency to grow thicker coats in the winter—and shed them in the summer—has also been documented in a variety of animals, including monkeys, cats, dogs, and camels. In humans, seasonal hair loss has been reported more in women than in men, Dr. Kwatra says, although the current study could not distinguish Google searches by gender.
According to the American Academy of Dermatologists, it’s normal to lose between 50 and 100 hairs a day. Noticing a little extra hair in the shower drain may be nothing to worry about, says Dr. Kwatra, especially if it’s during a warm-weather month.
But if those extra strands are enough to freak you out—or, ahem, send you to Dr. Google—it may be worth checking with your physician. About 40% of Americans suffer from unwanted hair shedding, and many women as well as men will notice an increase in hair loss as they get older.
In addition to seasonality, hair loss can be caused by a stressful event (like childbirth or a high fever), weight loss of more than 20 pounds, or a change in birth-control pills. Factors like diet, heredity, and thyroid levels can play a role as well.
Luckily, not all hair loss is permanent, and your doctor may be able to suggest remedies—like supplements or topical treatments—that may help to slow the process. Significant hair loss may also indicate another underlying health condition, says Dr. Kwatra, so it’s important to get checked out by a pro.