如果你觉得最近头发掉的厉害,那可能是这个原因
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 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. "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. |