The 10 Most Common Causes of Hair Loss

GoodRx / Maryann Mikhail, MD

Hair 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. 

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