Though some hair loss is typical with aging, sudden or excessive hair loss, or hair loss accompanied by a rash or itchy scalp, can be signs of a more serious condition. Here are some reasons women lose their hair, and what to do.

Inherited genes make follicles shrink and eventually stop growing hair. You may notice your part is gradually becoming wider or the hair near your temples has started to recede. As with men, genetics determine how much the condition affects you, though it’s rare for a woman to lose all of her hair.

“Unlike men who get a receding hairline or a bald spot, in women it’s often more diffuse, where the hair on the whole top area of the head is a little thinner,” Colavincenzo says.

▶︎ WHAT TO DO: A variety of treatments can help stop, slow or even reverse genetic hair loss, including over-the-counter minoxidil (Rogaine) and the prescription medication finasteride. Laser light therapy has also been shown to stimulate hair growth in men and women. And several studies have shown that platelet-rich plasma (PRP) injections—in which your blood is drawn, spun to extract red blood cells, then reinjected into the scalp—can significantly increase the number and thickness of hairs on your head.

“When there is a stressful event, your body says, ‘I’m going to stop devoting resources to hair growth and focus on this illness,’ ” says Lauren Eckert Ploch, M.D., a board-certified dermatologist in Aiken, South Carolina.

Called telogen effluvium, this condition happens a lot after people have COVID-19, Ploch says. You can also lose hair after major surgery or a large weight loss. Many people taking new GLP-1 drugs that treat obesity, such as Ozempic or Wegovy, experience hair loss. Psychological as well as physical distress can cause hair to fall out, another form of telogen effluvium, Colavincenzo says. She has seen patients shed hair after a divorce, the loss of a loved one or a layoff.

▶︎ WHAT TO DO: Telogen effluvium is temporary, Ploch says, and usually resolves by itself. Once the stress has passed, your hair should go back to normal in six to nine months.

Your thyroid is a butterfly-shaped gland at the base of your neck that plays a role in many bodily functions, including the development and maintenance of hair follicles.

Studies show that both an underactive thyroid and an overactive thyroid can contribute to hair loss. Women are more likely than men to develop thyroid problems.

▶︎ WHAT TO DO: Start with a visit to your primary care doctor, especially if you notice changes in your weight or energy level. A blood test can measure thyroid hormones, and medication can treat an overactive or underactive thyroid.

A shortage of vitamin D, iron, protein or other nutrients could contribute to hair loss.

“Vitamin or mineral deficiencies deprive the hair of necessary nutrients, weakening the hair structure and potentially interrupting normal hair growth,” explains Shoshana Marmon, M.D., assistant professor of dermatology at New York Medical College.

▶︎ WHAT TO DO: Talk to your health care provider for a basic blood test to check for nutrient shortages. It’s not necessary to take a supplement unless a deficiency is identified, Colavincenzo says. In fact, getting too much of certain nutrients such as vitamin A may cause you to lose hair.

If you often wear your hair in a tight ponytail, bun or braids, if you get regular chemical treatments, if you often wear a weave, or if you subject your hair to frequent heat styling, you can cause breakage and hair loss that can become permanent. “Less is more when it comes to hair care,” Ploch suggests.

▶︎ WHAT TO DO: Ploch recommends choosing ammonia-free hair color. Avoid wearing tightly pulled-back styles every day.

Alopecia areata is a complex autoimmune disease in which the immune system attacks your hair follicles, resulting in bald spots about the size of a quarter. A second disease, scarring alopecia, destroys hair follicles and replaces them with scar tissue.

▶︎ WHAT TO DO: See a dermatologist. Scarring alopecia can be treated with oral, topical or injectable anti-inflammatories or antibiotics. In the case of alopecia areata, newer drugs such as JAK inhibitors, which target the immune system, show real promise and may be more effective than older treatments such as steroid injections.