Hidden Causes of Hair Loss

Medically Reviewed by Debra Jaliman, MD on December 16, 2015
4 min read

One of the most challenging things about hair loss is figuring out why it’s happening. The list of causes ranges from genetics to medication to lifestyle. While it can be hard to pinpoint the cause right away, knowing the possibilities can help you figure it out.

Most of us can blame Mom and Dad for thinning locks, says Sonia Badreshia-Bansal, clinical instructor in dermatology at University of California, San Francisco, and a dermatologist who specializes in hair loss in women.

“Heredity is the most common cause of hair loss,” she says. “The gene can be inherited from either the mother's or father's side of the family, though you’re more likely to be affected if both of your parents had hair loss.”

Hereditary hair loss affects about 30 million women in the United States, the American Academy of Dermatology says. Women with this trait tend to develop thinning at the hairline, behind the bangs, or they might notice more scalp showing or a widening part, Badreshia-Bansal says. The condition develops slowly and may start as early as your 20s.

How to know for sure? A scalp biopsy can show if the hair follicles have been replaced with smaller follicles. That's a surefire sign of hereditary hair loss, she says. Applying minoxidil 2 % or 5% (Rogaine) to the scalp can stop further thinning, she says.

Telogen effluvium is a common type of hair loss translates to excessive shedding. (It’s normal to shed between 50 and 100 hairs a day.)

This type of hair loss can happen after your body goes through stress, says Amy McMichael, MD. She's the chair of the dermatology department at Wake Forest School of Medicine in Winston Salem, N.C.

Possible causes include:

Women with telogen effluvium typically notice hair loss between 6 weeks to 3 months after the stressful event. At its worst, handfuls of hair may come out.

Diet can play a role, too. Shortfalls in protein and iron can bring on telogen effluvium. So can extreme weight loss, says Paradi Mirmirani, MD, a dermatologist with Permanente Medical Group in Vallejo, Calif.

There are no tests for telogen effluvium, but your dermatologist may ask you about recent life events and look at the root of hairs you’ve shed. Club-shaped bulbs are a tell-tale sign, says Mirmirani, who's also a member of the North American Hair Research Society. The bulbs mean your hair has gone through a complete growth cycle, which may have sped up due to stress.

What can you do?

“In some cases, such as pregnancy or major surgery, reassurance and time is the best remedy,” she says. “If medication is the culprit, talk to your doctor about lowering your dosage or switching drugs. If it's stress-related, reduce anxiety.”

And if your diet isn't great, take steps to improve it.

Hair can start to regrow in about 6 months, if the cause of the effluvium is resolved. See more treatment tips for telogen effluvium.

Problems with your thyroid gland can lead to hair loss.

Hypothyroidism -- too little hormone -- may cause a host of symptoms, and hair, nails, and skin may become more brittle and break more easily," says Mirmirani. "With hyperthyroidism -- too much hormone -- hair loss can appear as metabolism speeds up.”

Blood tests can confirm whether you have a thyroid problem. Thyroid hormone medication may return your hormone levels to normal and help with hair loss and other symptoms. Your doctor will check every 6 weeks or so to see if you need to change your dosage. Learn about the difference between hair loss caused by a thyroid problem vs. male pattern baldness.

Hair loss can be caused by a fungus, psoriasis, or dandruff (seborrheic dermatitis).

  • The most common fungal infection affecting the hair is ringworm -- the same thing as athlete's foot. It requires an antifungal medication taken by mouth.
  • Seborrheic dermatitis makes your scalp shed, resulting in greasy, yellowish scales in the hair. Causes include hormonal changes or excess oil in the skin. It can be reversed. Treatment is usually a medicated anti-dandruff shampoo, a prescription antifungal cleanser, or steroid cream. Learn more about how dandruff can cause hair loss.
  • Psoriasis, an autoimmune condition, produces thick white scale on the scalp that can bleed if pulled off. Treatments include steroid creams, salicylic acid, coal tar, anti-inflammatory drugs, and biologics that suppress your immune system.

If you think you may have one of these conditions, talk to your doctor.

Alopecia areata is an autoimmune skin disease that causes hair loss on the scalp and body. It affects about 6.5 million people in the United States. It usually starts with one or more small, smooth circular patches on the scalp. It can progress to total hair loss.

Hair can grow back in or fall out again at any time; alopecia areata affects each person differently. The underlying cause isn't known yet, Mirmirani says. Genetics may make you more likely to develop it when activated by triggers like stress or illness.

Treatment usually involves corticosteroids or other medications that irritate the scalp and cause hair growth to restart. Other treatments such as finasteride,  photochemotherapy or laser can also be used.