10 most common causes of hair loss

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air loss can be devastating, but if you think your hair might be thinning, know that you are not alone. Hair loss is one of the most common issues dermatologists see, and treatment is possible in most cases. The first step is to figure out why it’s happening, and the key is to start early.

What is alopecia?

The medical term for hair loss is alopecia, regardless of the cause. Many people think it only happens to men, but it’s estimated that over half of all women will experience noticeable hair loss in their lifetime.

Signs that you might have alopecia are:

  • Hair thinning (which you might see in a thinner ponytail)
  • Bald spots that grow over time
  • A receding hairline and/or loss of clear edges
  • A widening hair part

It’s normal to lose 50 to 100 hairs a day. Much more than that could mean there is excess shedding. Certain causes of hair loss can cause specific hair patterns and symptoms. Read on to learn more about common causes below.

1) Age

Almost everyone will notice hair loss and hair thinning as they age. Our cells continually grow and die off at all ages, but when we’re older, our cells die off more quickly than they regenerate. It’s why we get weaker bones and thinner skin. And it’s a similar process for our hair.

As we age, we also produce less oil in our scalp, which can make our hair weak and brittle. This can also contribute to an overall hair loss and thinning.

Some people may experience more severe hair loss with age in a condition known as androgenetic alopecia, or pattern hair loss. We’ll talk more about that below.

2) Genetics

The most common type of hair loss, androgenetic alopecia, is hereditary and related to age. It’s commonly referred to as male or female pattern hair loss, and it affects more than 50 million men and 30 million women in the United States. This is a more extreme form of hair loss that usually begins in young adulthood and gradually progresses with age.

For males, this type of hair loss often starts at the temples and expands to the top of the scalp. There may also be a little thinning at the top of the head.

For females, it usually first becomes noticeable where you divide your hair, but there’s gradual thinning all over. The hairline typically stays the same, but the hair part can widen.

You may have heard that this kind of hair loss is inherited from your mother’s side of the family, but researchers have discovered that a number  of genes affect how likely you are to experience pattern hair loss. One such gene affects how your hair follicles respond to hormones known as androgens (which are sometimes called “male hormones”).

3) Hormonal changes

People with conditions like polycystic ovary syndrome (PCOS) and congenital adrenal hyperplasia (CAH) have higher androgen levels, which can cause female pattern hair loss. If you are a women who experiences more obvious hair loss and any of the following symptoms, you may want to ask your healthcare provider about having your hormone levels tested:

  • acne
  • excess hair growth on the face or body
  • irregular periods

Other things that can cause dramatic changes in your hormone levels — like pregnancy, childbirth, menopause, and hypothyroidism — may also affect hair growth. Even changing medication routines can cause your hair to become thinner if your medications affect your hormone levels. For example, some women who stop taking birth control pills can experience hair loss. Fortunately, in most of these cases, you can slow down or reverse the hair loss with proper treatment.

4) A stressful life event

Out of nowhere, you notice a lot of hair falling out. You see it on your pillow, on the floor, on your clothes, and stuck in the shower drain. Hair seems to come out so easily, you’re afraid to brush it. The medical term for this is telogen effluvium.

During a telogen effluvium, it might feel like you are going to go bald. Rest assured — you won’t. Telogen effluvium is a response to stress. Excess hair shedding starts 2 to 3 months after a stressful physical or emotional event and peaks about 4 to 5 months later. Over time, your body readjusts and the hair gradually stops falling out. Within 6 to 9 months, things go back to normal.

Stressful life events like losing a loved one, going through surgery, or being diagnosed with a serious illness can all increase your risk for hair loss. But hair loss itself can be stressful, too, which can lead to a vicious cycle. Remember: Telogen effluvium is temporary — you will not go bald from it, and your hair will come back. In most cases, no treatment is necessary.

5) Nutritional deficiencies

A chronic form of telogen effluvium can occur. This type of hair shedding starts slower and lasts longer (over 6 months). Possible causes are often related to nutritional deficiencies. Having low levels of iron, vitamin D, and zinc have all been shown to be linked to hair loss.

Vitamin deficiencies are usually easily corrected with dietary supplements. It’s important to always talk to your provider before you try any new supplements.

6) Autoimmune disease

Alopecia areata is a form of hair loss that is autoimmune. The body’s immune system attacks healthy hair follicles, causing them to fall out.

While having your hair done, your hairdresser may find a round patch of hair loss on your scalp. Or, you may notice a space in your eyebrows or a cluster of missing eyelashes. If you are a man, you may notice a bare patch in your beard. These scenarios are common in alopecia areata. Researchers often link it to periods of high stress.

Most often, alopecia areata shows up as one or more coin-sized, hairless patches. It can affect any hair on the body. In rare cases, it can be more severe. In alopecia totalis, hair loss happens to the whole scalp. In alopecia universalis, it affects the whole scalp, face, and body.

The good news is that the hair follicles are still alive. In most cases, the hair comes back on its own over time. However, there is no known cure, and it’s common for alopecia areata to come back over and over again.

Injections of cortisone into the scalp by your dermatologist can speed up recovery. For people with more severe hair loss, light therapy and medications are available.

7) Infections

Infections can affect the scalp and cause hair to fall out. This happens when bacteria, yeast, or fungi overgrow and invade hair follicles. You might see pus bumps, redness, and scaling. The scalp can feel itchy or even painful. If you notice any of these symptoms, see your dermatologist right away.

Fungal infections of the scalp are highly contagious, and are the most common cause of hair loss in children. To prevent it, children should avoid sharing hats and scarves.

When you see a healthcare provider for treatment, they’ll need to figure out what kind of bug is causing it. They might need to take a swab sample and send it to the laboratory to know for sure. The right treatment will depend on whether you’re dealing with bacteria, yeast, or fungi.

Most scalp infections are curable with the right antibiotic or antifungal medication. Without treatment, these infections can lead to permanent scarring.

8) Medications

Certain medications can cause hair loss as a side effect. It doesn’t happen to everyone taking these medications, but hair loss can happen with some popular ones, including:

  • Some cholesterol-lowering medications (e.g., atorvastatin, simvastatin)
  • Some blood pressure medications (e.g., captopril, lisinopril)
  • The antacid cimetidine (Tagamet)
  • The gout medication colchicine (Colcrys)
  • The acne medication isotretinoin (Accutane)
  • The steroids testosterone and progesterone

Consult your provider if you notice hair loss when you start taking a new medication. They can tell you whether another medication might be better for you and give you instructions on how to safely stop taking your current medication, if needed.

9) Traumatic hair styling and inflammation

So far, we have discussed non-scarring types of hair loss, where the hair follicles are still alive and hair can regrow. This is in contrast to scarring hair loss, where hair follicles are destroyed and hair cannot regrow.

Inflammation is the ultimate cause of scarring hair loss. The scalp might appear red. Common symptoms include itching, burning, and pain. Infections and certain inflammatory skin conditions can cause hair follicle destruction. Traumatic hair styling practices like heat styling, chemical hair treatments, and tight hairstyles can also cause scarring hair loss.

With hair loss caused by inflammation, you want to stop the inflammation in time to prevent irreversible damage. Most often, dermatologists will do this with specific medications, depending on the cause and how bad the hair loss has gotten. Unfortunately, many people delay seeking treatment and end up with permanent scarring. Cortisone injections, along with topical minoxidil, can stimulate some hair growth. If the scarring is extensive, a hair transplant might be an option.

10) Chemotherapy and radiation

Hair loss can be a very real fear for many patients who have received a diagnosis of cancer and need to undergo chemotherapy or radiation. Cancers are due to cells that grow too quickly. Chemotherapy drugs are often used to kill off these cells, so they don’t form tumors or spread. However, because cells in your hair follicles also grow quickly, chemotherapy can affect your hair, too.

Radiation therapy, also used in cancer treatment, can also cause hair loss. But while chemotherapy can cause hair loss throughout the body, radiation therapy usually only affects the area that’s treated.

With both types of treatments, hair loss is generally temporary, and you can expect your hair to regrow in a few months’ time.

The bottom line

If you are experiencing hair loss, don’t panic. Your first course of action should be to see a board-certified dermatologist as soon as possible. It’s best not to waste time on home remedies and hair supplements that may or may not work. In fact, they can do more harm than good.

When you see your dermatologist, they’ll need to determine the cause of your hair loss first. This may include a physical examination of your hair and scalp; blood tests to uncover issues like thyroid problems or vitamin deficiencies; or a scalp biopsy, where a small piece of scalp is taken under local anesthesia and sent to the lab for investigation.

Once your provider knows the cause, they’ll give you treatment options. The sooner you start the right treatment, the better chance you have of regrowing your hair. Hair loss may not always have a cure, but in many cases, medications can help if you use them early enough.


Maryann Mikhail, MD
Dr. Mikhail is a board-certified dermatologist in the Dr. Phillip Frost Department of Dermatology and Cutaneous Surgery at the University of Miami Miller School of Medicine.

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