8 Possible Reasons Your Hair Is Falling Out (2024)

Hair loss can be such a sneaky thing: One minute all strands are reporting for duty; the next, it seems, your ponytail is half the size and…wait, is that a bald spot? And with so many potential causes of hair loss, figuring out why yours is falling out, let alone what to do about it, can be a long and frustrating journey.

Before we get into the nitty-gritty, let’s start with a crash course on how hair grows in the first place. As the National Library of Medicine (NLM) explains, the process can be broken down into three phases: growth (anagen), during which new strands sprout from your hair follicles; transitional (catagen), which marks the end of active growth; and resting (telogen), when your follicles go on hiatus and shedding ensues.¹

It’s normal to lose anywhere between 50–100 hairs a day, according to the American Academy of Dermatology (AAD). Any more than that—especially if you also notice changes in the texture or thickness of your strands—could indicate that your body’s sending up a flare. “The aging process undeniably contributes to changes in the hair growth cycle, such as slowing down the rate at which it grows, but seldom acts as the only cause of substantial hair loss,” Hope Mitchell, MD, a board-certified dermatologist and the founder of Mitchell Dermatology in Ohio, tells SELF.²

So what other factors, aside from getting older, can contribute to significant thinning? We asked experts to break down the most common underlying causes of hair loss in women.

1. Genetics

Androgenetic alopecia is the most common cause of hair loss worldwide, per the AAD. In people assigned female at birth, the condition is better known as “female pattern hair loss.” It’s a hereditary issue that’s triggered by a one-two punch of genetic and hormonal factors, Dr. Mitchell explains. Essentially, people with this condition have inherited genes—from either or both of their parents—that are extra sensitive to androgens, hormones that play a major role in regulating hair growth. Androgens are typically referred to as “male” sex hormones, even though everyone produces some level of them.^{3 4}

Some researchers theorize that one of these hormones in particular, called DHT, latches onto the androgen receptors in hair follicles and overstimulates them.⁵ This can trigger a gradual shrinking of the follicles over time, which “causes the affected hair to become finer and shorter with each growth cycle, eventually leading to a reduction in hair density [the number of strands per square inch of scalp],” Dr. Mitchell says. The growth phase becomes shorter too, so not only might you experience an uptick in shedding, but you might also notice strands that don’t grow as long as they once did.³

How much of a role androgens play in driving female pattern baldness, specifically, is still being sussed out by researchers: Past studies have found that hair loss in women can strike even when androgen levels are normal, which suggests other unknown factors are also involved.⁵

What you’ll probably notice

One of the first obvious signs of hereditary hair loss for people assigned female at birth is a wider part, per the AAD. As the condition progresses, you might also experience widespread thinning, though the frontal hairline (outlining your forehead) usually stays intact, Dr. Mitchell says.

2. Intense stress

Stress-induced hair loss is called telogen effluvium and can strike as a result of—you guessed it—intense stress, both physical (think: giving birth or having major surgery) and mental or emotional (losing your job or a loved one, for example). You may experience a temporary halt in hair growth as your body puts its resources toward getting you through the underlying stressor. A large portion of follicles simultaneously shift into the resting phase, with this pause lasting anywhere from three to six months. Once your body decides the coast is clear and the growth phase resumes, the hairs that have been suspended in the resting phase enter the shedding phase.⁶

According to the NLM, other stressors that can trigger telogen effluvium include high fever, severe infections (like COVID-19), rapid weight loss, and stopping certain medications (like beta-blockers, antidepressants, and birth control pills, in particular).

Another sneaky culprit that might be stressing out your insides? Nutritional deficiencies, like a lack of iron, vitamin D, biotin, or zinc. “These nutrients play roles in cellular processes that are essential for maintaining the hair growth cycle,” Dr. Mitchell says. So running low on them could cause disruptions to these processes and result in shedding or thinning.⁷

What you’ll probably notice

This type of hair loss is technically excessive hair shedding, a generalized thinning all over your scalp rather than specific bald patches. “There’s typically a three-month delay between the stressful event and the onset of excess shedding,” Kristen Lo Sicco, MD, associate professor of dermatology and director of the skin and cancer unit at NYU Langone Medical Center in New York City, tells SELF—at which time you might start noticing handfuls of hair in your brush, in the shower drain, and on your pillow.

3. Supertight hairstyles

Sporting über-restrictive hairstyles on the regular can trigger traction alopecia—hair loss caused by persistent tension or pulling on your hair. Per the AAD, tension-inducing hairstyles include: Buns, ponytails, and up-dos that are tightly pulled back; cornrows or braids; dreadlocks; hair extensions or weaves.

Perma-tugging on your hair can lead to damage and inflammation around the follicles, disrupting the normal growth cycle, Dr. Mitchell says. The result? Weakened follicles and eventual hair loss that can become permanent.⁸

What you’ll probably notice

One of the most common indicators of traction alopecia is thinning hair along the frontal hairline or sides of the scalp, where tension from hairstyles is most concentrated, Dr. Mitchell says. This might look like a widening of the part or receding hairline, as well as short, broken hairs along the affected areas. (If you’re more of an extensions gal, indicators like these are more likely to show up on the back of your scalp, she adds.)⁹

4. Harsh hair styling habits

If heat styling or chemical treatments are part of your regular hair-care routine, this puts you at risk of harming your strands and potentially developing a hair shaft disorder called trichorrhexis nodosa—a condition in which damaged, weak points in the hair shaft cause strands to break off easily.

5. Severe dandruff

There’s dandruff and then there’s its more severe cousin, seborrheic dermatitis: A pesky skin condition characterized by a rash (that may look darker, lighter, or redder than the surrounding skin), as well as itchy and flaky patches that set up shop in spots with a lot of oil glands, including your scalp. “It’s driven by an inflammatory response against organisms that live on our scalp—specifically Malassezia yeast colonies,” Dr. Lo Sicco says.¹¹

These flaky patches, combined with the oil that’s produced by the scalp, can clog your follicles, ultimately impairing the hair’s nutrient supply and weakening its structure (not to mention the subsequent damage—and shedding—that can happen when you constantly scratch your head).¹² Meanwhile, the inflammatory response disrupts the normal hair growth cycle and can trigger telogen effluvium, Dr. Mitchell explains, where, again, your hair follicles go on strike for an extended period, only to later shed in bulk.

What you’ll probably notice

Aside from the whole inflamed scalp thing, this type of hair loss isn’t usually associated with dramatic balding, but with a gradual reduction in hair density—particularly in the form of increased shedding wherever the seborrheic dermatitis is giving you the most trouble. “The hair itself may also become finer and more fragile due to the inflammatory processes disrupting the growth cycle,” Dr. Mitchell says.

6. Inflamed hair follicles

Folliculitis is a skin condition that strikes when hair follicles become inflamed—say, from physical irritation (shaving, traction, wigs) or an infection (bacterial, fungal)—which compromises the integrity of the follicles.¹³

There are two main types of folliculitis: superficial and deep. The former involves only part of the hair follicle and will likely heal within a few days, whereas the latter consumes the entire follicle and tends to be more severe and long-lasting.

“As the follicle becomes inflamed, damage can happen to the surrounding tissues that disrupt the normal hair growth cycle,” Dr. Mitchell says. “In severe cases, the infection may lead to scarring, causing permanent hair loss.”

What you’ll probably notice

The particular type of folliculitis you experience will depend on the underlying cause (friction or infection), but “it typically presents as small acne-like bumps or pustules surrounding the affected hair follicles,” Dr. Mitchell says. “These may be itchy, tender, or painful, and in some cases form clusters that resemble a rash.” As the condition progresses, you might start noticing the surrounding skin becoming irritated and darker, lighter, or redder too.

7. Hormonal imbalances

Hormonal changes can be a contributing factor to hair loss in women, particularly the high and fluctuating androgen levels associated with polycystic ovary syndrome (PCOS) and perimenopause, respectively.

PCOS is a hormonal condition that messes with ovulation, causing issues like irregular periods and infertility. Another pesky symptom is thinning hair, thanks to elevated androgen levels (remember DHT?) and the hair follicle shrinkage that typically follows. Cue thinner, more brittle hair.¹⁴

The hormonal fluctuations that happen during perimenopause (the transitional period before menopause), can disrupt the hair growth cycle in a similar way. “Estrogen, which supports hair growth, decreases, while androgen levels may remain relatively stable,” Dr. Mitchell says. When androgen levels become more dominant as a result of these estrogen dips, this can encourage hair thinning.¹⁵ That’s why hormone therapy that increases androgen levels can also cause shedding.¹⁶

What you’ll probably notice

People with hormonal imbalances like these typically experience hair loss similar to that of androgenetic alopecia, Michele Green, MD, a board-certified dermatologist based in New York City, tells SELF. You might notice your hair thinning out along the top of the head and sides of the scalp, your part getting wider, and your strands becoming finer and more prone to breakage.¹⁴

8. Autoimmune diseases

When you have an autoimmune disorder, your immune system essentially turns on you and attacks healthy body tissue by mistake. Doctors have yet to nail down why this happens (and, of course, the specific causes of any condition are highly individualized), but one theory is that certain types of infections or drugs may trigger changes in the body that cause the immune system to trip up.¹⁷

One such disorder is alopecia areata, in which the immune system mistakenly attacks the hair follicles. Another is discoid lupus erythematosus (DLE), a type of lupus that targets the scalp and can lead to permanent hair loss, Dr. Lo Sicco says. Conditions that primarily affect another part of the body—like thyroid disease, rheumatoid arthritis, or sickle-cell anemia—can also cause hair loss as one of many symptoms.

What you’ll probably notice

Alopecia areata commonly presents as round bald patches on the scalp. “In more severe types, like alopecia totalis, it can cause complete scalp hair loss,” Dr. Lo Sicco says.¹⁸ As for DLE, lesions can develop that are darker, lighter, or red and inflamed, with a scaling and crusty appearance. According to the American Osteopathic College of Dermatology, the center of these scaly patches may appear lighter in color with a rim that’s darker than the surrounding skin.

When hair loss is just one of many symptoms versus the primary outcome of an autoimmune disorder, how it presents depends on the underlying condition itself. Thyroid disease typically causes excessive shedding, for instance, while rheumatoid arthritis tends to trigger overall thinning.¹⁹

When to see a dermatologist about your hair loss

Most cases of telogen effluvium (excessive shedding) will gradually resolve on their own without treatment—usually within six months or so, Dr. Lo Sicco says. If your hair doesn’t return to its normal fullness within this time frame or, rather than overall shedding, you’re noticing a widening at your part, bald spots, or thinning along your hairline or crown, then it’s time to see a dermatologist if you can. An expert can get to the bottom of what’s going on, whether that be chronic shedding or full-on hair loss. And, as we mentioned above, if you have other worrying symptoms, like itching, pain, burning, flaking, or discolored rashes, seek help sooner.