The 10 Most Common Causes of Hair Loss

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Hair loss can be devastating. If you think your hair might be thinning, know that you're 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 the cause of your hair loss. And the key is to start treatment early.

What is alopecia (hair loss)?

The medical term for hair loss is "alopecia," regardless of the cause. Many people think it only happens to men, but women of all ages can experience hair loss. Although you can't die from alopecia, hair thinning can be life altering and devastating for people who experience it.

It's totally normal to lose about 50 to 100 hairs a day. But losing more than that may mean there is excess shedding. When you lose more than you replace, you'll start to see signs of hair thinning and hair loss.

Signs that you could have abnormal hair loss 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

There are different causes of alopecia, and some are hereditary (they tend to run in families). Certain causes of hair loss can cause specific hair patterns and symptoms. So your provider may be able to diagnose it just by looking at your scalp and asking you some questions.

In other situations, they may need to do a small skin biopsy (where they take a small skin sample to evaluate under a microscope). Depending on the cause, alopecia may be curable or reversible, so getting diagnosed and treated early is important.

Let's take a closer look at 10 common causes of hair loss.

1. Age

Almost everyone will notice hair loss and hair thinning as they age. Cells continually grow and die off at all ages. But with age, cells die off more quickly than they regenerate. This is why people get weaker bones and thinner skin. And it's a similar process for hair.

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

Some people may experience more severe hair loss as they age. This condition is androgenetic alopecia, which is also called female- or male-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 affects more than 50 million men and 30 million women in the U.S. This is a more extreme form of hair loss that usually begins in young adulthood and gradually progresses with age. It can have different patterns depending on who it affects:

• Male-pattern 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.

• Female-pattern hair loss 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 research shows that a number of genes affect how likely someone is to have this type of hair loss.

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.

You may want to ask your healthcare provider about having your hormone levels tested if you're a woman who experiences more obvious hair loss and any of these symptoms:

• Acne

• Excess hair growth on the face or body

• Irregular periods

Other things that can cause dramatic changes in hormone levels - like pregnancy, childbirth, menopause, and hypothyroidism - may also affect hair growth. Even changing medication routines can cause your hair to thin 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. Stressful life events

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 that you may be afraid to brush it. The medical term for this is "telogen effluvium."

During telogen effluvium, it might feel like you're going to go bald. Rest assured - this won't happen. 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, the body readjusts and 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 the risk for hair loss. But hair loss itself can be stressful, which can lead to a vicious cycle.

Most cases of telogen effluvium are temporary and don't require treatment.

5. Nutritional deficiencies

In some situations, hair loss can happen because of nutritional deficiencies. Low levels of iron, vitamin D, and zinc have all been linked to excessive shedding and hair loss.

In most cases, dietary supplements can easily correct vitamin deficiencies. Your provider will usually do a blood test before recommending a supplement, so it's important to talk to them before starting any new supplements.

6. Autoimmune disease

Certain autoimmune conditions can cause hair loss when inflammation in the body attacks healthy hair follicles, causing hair to fall out. Depending on how severe it is, hair loss can be temporary or permanent. Here's a look at two more common conditions:

• Alopecia areata usually shows up as one or more coin-sized, hairless patches. These can happen anywhere on the body. It can be mild (just a few patches), or it can affect the whole scalp, face, and body. There is no cure. But, in most cases, the hair comes back on its own over time. Different treatments, like steroid injections or the new medication Olumiant (baricitinib), can help hair to regrow faster.

• Lupus erythematosuscan affect many parts of the body, including skin and hair. Some people with lupus may experience thinning hair throughout their scalp. Others may notice hair loss associated with a rash that is thick, scaly, and red or brown in color. Depending on the type of hair loss, hair may regrow when the underlying lupus is treated.

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 they're the most common cause of hair loss in children. To prevent it, children should avoid sharing hats and scarves.

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 thinning as a side effect. It doesn't happen to everyone who takes these medications, but hair loss can happen with some popular ones, including:

• Some cholesterol-lowering medications (like atorvastatin and simvastatin)

• Some blood pressure medications (like captoprilandlisinopril)

• The antacid cimetidine (Tagamet)

• The gout medication colchicine (Colcrys)

• The acne medication isotretinoin (Accutane)

• The steroids testosterone and progesterone

Tell your prescriber right away if you notice hair loss after you start a new medication. They can recommend a change to something else and help you stop the problem medication safely.

9. Traumatic hairstyling

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 can't regrow.

Some hairstyling practices can cause this type of scarring hair loss. If they're not stopped early, they can cause significant hair loss that can't be regrown. Examples of these practices include:

• Heat styling

• Chemical hair treatments

• Tight hairstyles

Some shampoos that contain the chemical formaldehyde have been linked to hair loss, too. If you notice hair loss after starting a new shampoo, stop using it and try a different product after making sure it doesn't have any formaldehyde in it.

10. Chemotherapy and radiation

Hair loss can be a very real fear for many people who have received a diagnosis of cancer and need chemotherapy or radiation. Chemotherapy drugs kill cells in the body that grow quickly so that they don't form tumors or spread. But, because cells in hair follicles also grow quickly, chemotherapy can also affect hair.

Radiation therapy, another 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. So you can expect your hair to regrow a few months after the end of treatment.

When hair loss is a sign of something serious

Most hair loss is related to aging or genetics. But sometimes it can signal a more serious underlying medical problem. Get checked out by your provider if your hair loss is associated with any of these signs:

• A new red or brown, scaly rash on your face or body could be a sign of lupus erythematosus.

• Feeling very cold or tired all the time may signal hypothyroidism.

• Unexpected weight loss might mean a protein deficiency.

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