What You Should Know About Seasonal Hair Loss

You're brushing your tresses — glamorously and in slow motion — when suddenly you notice that a full thicket of hair is now in your hand or entangled in your brush. Your initial reaction is, of course, terror. You immediately jump to the worst scenario: All my hair is falling out! But before you start panic-Googling "hair loss" or "sudden baldness," relax and read on.

The life of a hair can be divided into three phases. In the anagen phase, hair grows about half an inch a month for an average of two to six years. Next comes the short, transitional catagen phase, which lasts only about 10 to 14 days. Finally, hair enters the telogen, or resting, phase, where it is released and falls out. The hair follicle takes a break for about three months, after which it begins anew in the anagen phase. Each strand of hair on your head is at a different place in its life cycle, Dr. Angela Phipps, Medical Advisor to Hair Club, explained to Bustle. About 90 percent of hair is in the anagen phase, 3 percent in the catagen phase, and the rest in the telogen phase (per Stylecaster).

When greatest hair loss occurs

An average head of hair has 100,000 strands (via Stylist). Normally, about 50 to 100 hairs fall out each day. But there are further differences in normal hair loss among ethnicities and types of hair. According to Diane Minar, a senior scientist at Unilever, while Caucasians can lose up to 100 strands a day, Asian people lose about 70, and Black folks about 60. Blonde hair loss is greater than the loss of darker hair, and longer hair may appear to shed more, but it's the length of the hair taking up more visual space.

But what if you think you're shedding more than 100 strands a day? There's such a thing as seasonal hair loss, when the number of strands lost increases temporarily. According to one hair expert, hair loss up to 150 strands a day can still be considered "normal" (per Refinery 29).

Past studies have found there is a seasonal pattern to hair loss, with the highest number of hairs in the telogen phase (therefore, greater hair loss) occurring in the summer, or maximal hair shedding taking place in August and September. A more recent study published in 2017 that looked at Google Trends data across eight countries over 13 years determined that search terms such as "hair loss" trended highest in the summer and, to a lesser extent, in the fall.

Why does summer seem to lead to more hair loss?

Why hair loss is greater in the summer months and going into the early fall isn't known — but there are theories. Like so many other human characteristics, evolution may play a role in seasonal hair loss. It's possible the scalp needs less protection from the sun in the winter. Or an abundance of summer shedding may be due to the fact that hair provides warmth, which is unnecessary in the heat. Still another theory is that the stress of summer heat may cause hair to fall out in greater numbers.

Whatever the reason, there's no doubt seeing a larger clump of hair in the shower drain is scary. But check the calendar first. If it's summer or early fall, you're probably experiencing normal seasonal shedding. But if you notice bald spots, hair is coming out in chunks, or your scalp is irritated or inflamed, it's recommended you check with a dermatologist.