What causes hair loss—and what you can do about it

The words “hair loss” typically bring to mind Rogaine ads and men with the textbook horseshoe hair pattern of baldness—not young women with seemingly flowy, waist-length hair. But it turns out that the condition of hair loss does not discriminate—it can happen to anyone, at just about any age.

Just ask thousands of young women worrying about the amounts of hair dropping into the shower drain, or buying bottles of hair-growth supplements and thickening shampoos by the keg…

While men’s hair loss is “generally pretty straightforward genetics,” says Carlos Wesley, MD, a hair-health genius who specializes in its restoration, “women come in [to my office] at all different ages and stages of hair loss, and there are a lot more possibilities that could lead to women’s hair loss.” So it’s not as easy to predict or determine the cause. (Frustratingly.)

“Often when young women come in with significant hair thinning, you have to think about a bunch of things,” says Dr. Wesley, endocrine abnormalities being one of them. So before we explain the root causes (ahem) of thinning hair, it’s important to understand some basic science about hair itself.

Keep reading to learn some surprising things about your tresses and how to keep them healthy.

Hair 101

“We’re all born with 100,000 hair follicles on our head, and each of those follicles is pre-programmed to go through a certain number of cycles throughout our lifetime,” explains Dr. Wesley. “Your hair grows, plateaus, and falls out. Every time it grows back in, it grows back a little thinner, a little finer.”

When we’re babies (before we even care about issues such as hair volume or beach waves), our hair follicles are just single hairs. “As we get older, they increase with each cycle, and by age 12-14 we have big, voluminous hair because our hair bundles are in clusters of four or more,” says Dr. Wesley. “This is when we’re all candidates for our best hair. But over time, that process reverses itself—which is the gradual thinning process over our lifetime.”

The thinning leads to less volume on the top of your scalp, which is hard to notice. “It’s not something we really pick up on,” says Dr. Wesley, because it’s very gradual. “You’d only notice at a loss of about 50 percent of your overall hair volume.”

So what’s the difference between a regular hair shedder (I tend to send tons down the drain with every shower) and someone suffering from real hair loss?

“Every single one of us has about 100 strands of hair fall out every day—that’s normal—and 100 new hairs grow in,” he says. Anyone else breathing a huge sigh of relief? “We just see the hair falling out because they’re full-length. We don’t see the ones coming in because they’re so short,” explains, Dr. Wesley.

Now, for the culprits behind hair loss. Keep scrolling for the 4 biggest reasons—and natural ways to counteract them.

1. Hormones

As with common cases of adult acne and bloating, hormones are to blame for many annoying women problems—hair not excluded. “Thyroid problems or polycystic ovarian syndrome can cause fluctuations in hormones (particularly androgens, the male hormone),” says Dr. Wesley, which can lead to hair loss. Estrogen is key for protecting your hair, he says, which is why some doctors suggest taking birth control pills. “They can have a high impact on hair,” confirms Dr. Wesley.

2. Your diet

Another cause of hair loss? Crash dieting. “It can manifest itself in hair thinning,” says Dr. Wesley—whose staff one year made a New Year’s pact to aggressively cut calories and by April were all experiencing hair thinning. “After they went back on a healthy diet, their hair grew back.”

A fundamental element of a hair-friendly diet is getting plenty of iron. Wesley advises women who experience hair thinning to take a ferritin test, which looks at your body’s ability to take iron and store it. “It’s a really important co-factor in hair growth,” says Wesley. A ferritin level below 70 is low. Wesley suggests incorporating an iron supplement into your diet. (Another great supplement for luscious locks? Biotin, according to Wesley.)

Good cholesterol and protein are also key. “Cholesterol is really healthy to have in your diet,” says Wesley. He advises to eat whole eggs—not just egg whites.

3. Acne medications

Strong acne medications—especially Accutane—can lead to hair thinning as a side effect. “Accutane can cause your hair to go through a cycle a little bit faster, and even though it comes back in, it comes back in a little finer,” says Dr. Wesley. Another good reason you might want to opt for regular facials and natural acne-fighters like plants or facial oils.

4. Emotional stress

Sometimes we jokingly say that a certain stressful event or task is making our hair fall out. But this expression comes from the facts: “Emotional stress is something that can cause cortisol (the stress hormone) levels to be high,” says Dr. Wesley.  “A death in the family, a breakup, job stress, divorce—all of these things can expedite the hair thinning process because cortisol pushes the hair cycle forward. It’s not a myth.” All the more reason to take up meditation, right? A happy mind can lead to a happy head (of hair).

Originally published August 22, 2016; updated July 17, 2018.

Now that you know how to keep your hair health in check, how to wear it? Try one of these 11 ways to rock the high ponytail, or maybe opt for super-cute boxer braids.