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What causes hair loss? Diagnosis, prevention, and treatment

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician
Updated Apr. 10, 2024  •  Published Jun. 15, 2023
Fact Checked
Hair loss causes

Overview: What is hair loss?

Hair falls out every day as part of its natural growth cycle. New hair quickly grows back. However, sometimes hair comes out faster than it’s replaced, causing hair loss or, in medical terms, “alopecia.” Hair loss can occur in many ways. The hair can fall out at the roots or break. Hair loss can happen slowly, like a receding hairline. On the other hand, hair can fall out quickly or in clumps. Hair loss can occur anywhere on the body: the head, face, underarms, back, groin, legs, eyelashes, or eyelids. Sometimes hair loss can occur everywhere all at once. Hair loss can sometimes be more or less permanent, like male pattern baldness. Sometimes it’s temporary, such as hair loss due to cancer treatments. It all depends on the cause. 

Key takeaways:

  • Hair loss is a common health condition that can affect anyone regardless of age, sex, race, or ethnicity. 

  • Hair loss is caused by aging, male hormone sensitivity (androgenetic alopecia), stress, traction (pulling on the hair), infections, autoimmune disorders, hormone imbalances, medications, trauma, and chronic illness. 

  • Risk factors for hair loss include male sex, advancing age, family history of hair loss, stress, hair pulling, hairstyles, prescription drugs, steroid use, exposure to infections, and chronic illness.

  • Hair loss symptoms include patterned or generalized thinning hair (alopecia), patchy hair loss, or hair falling out in clumps (effluvium).

  • Hair loss is typically self-diagnosable.

  • Hair loss generally does not require treatment. It may or may not resolve, depending on the cause. If it does resolve, the timeline for hair restoration will vary depending on the cause.

  • Hair loss treatment may include treatments for the underlying cause, discontinuing medications that cause hair loss, correcting vitamin or iron deficiencies, hair regrowth medications, corticosteroids, or immunosuppressants. Read more about hair loss treatments here.

  • Hair loss may be prevented by gentle hair care, a healthy diet, stress reduction, and avoiding harm to the skin.

  • Use coupons for hair loss treatments, like Rogaine (minoxidil), Propecia (finasteride), and dutasteride, to save up to 80%.

What causes hair loss?

The most common cause of hair loss is aging combined with testosterone sensitivity (androgenetic alopecia):

  • Male pattern hair loss

  • Female pattern hair loss

Approximately 50% of men and women will experience androgenetic patterned hair loss as older adults.

Medical conditions that cause hair loss include:

  • Infections, particularly fungal infections such as tinea capitis

  • Cancer

  • Autoimmune conditions, including scalp psoriasis and lupus

  • Alopecia areata (an autoimmune reaction in which the immune system attacks hair follicles)

  • Hormone imbalances, including thyroid disease and childbirth

  • Severe chronic illness

  • Injury to the skin, including burns and chemical damage

  • Chemotherapy

  • Drug side effects

  • Steroid use

  • Poor nutrition, particularly iron deficiency, and vitamin D deficiency

  • Physical stress including surgery

Hair thinning and hair loss can also be due to behaviors or lifestyle. Hair loss is usually reversible, but not always. Reversible hair loss causes related to lifestyle or habits include:

  • Emotional stress

  • Excessive hair brushing or shampooing

  • Tight hair styling (traction alopecia)

  • Using certain types of hair products

  • Hair styling processes

  • Scratching the scalp too much

  • Compulsive hair pulling (trichotillomania)

  • Crash dieting 

RELATED: Why is my hair falling out? Learn the causes of hair loss

Risk factors for hair loss

There are as many risk factors for hair loss as there are causes. 

The most common risk factor for hair loss is growing older, since both male pattern and female pattern baldness will happen to at least half of us.

The most common risk factors for developing hair loss due to medical conditions include:

  • Autoimmune disorders

  • Allergies

  • Skin conditions such as dermatitis

  • Cancer

  • Chronic illness

  • Exposure to scalp infections from sharing hats or living in a warm, humid environment

  • Side effects of some prescription drugs

Common risk factors for losing hair due to lifestyle or habits include:

Is hair loss serious? When to see a doctor

Hair loss is not a health-threatening condition, but it is often distressing and could be a sign of a more serious medical condition. While hair loss due to aging is only partly reversible, some types of hair loss can be restored through treatment. So while hair loss may not be serious, see a healthcare professional if the hair is falling out in clumps, thinning for no apparent reason, accompanied by other symptoms, or if the hair loss is causing significant distress. 

How is hair loss diagnosed?

While hair loss is not a diagnosis, a healthcare professional will try to identify the underlying problem. In many cases, a medical history and physical examination will be enough to make a diagnosis.

The first step is to determine the type and extent of hair loss. Be prepared to tell the clinician when the hair loss started and where it’s happening. The clinician must know if the hair is coming out at the roots or breaking. The clinician will also want to know if the hair loss has been gradual or rapid and any other symptoms. 

The clinician will examine the places on the skin where hair is thinning or falling out, usually the scalp. They’ll look for bald patches, scarring, or possible injuries. The clinician may do a complete skin examination. During the physical exam, the clinician can perform a few simple tests like pulling on the hair to see if it comes out, gently trying to break hair in the middle (called a tug test) or parting the hair to examine newly growing hair strands (a card test). Hair that is pulled out may be examined under a microscope to determine what growth stage the hairs are at when pulled out.

If another cause is suspected, such as a fungal infection or hormone disorder, other tests may be necessary, including blood tests or a skin biopsy to examine the area of hair loss under a microscope.

Is hair loss hereditary?

Genetics plays a significant role in male pattern and female pattern hair loss. Though hair loss may be predicted from family members, it’s not 100% correct. Heredity also plays a role in autoimmune diseases like psoriasis or alopecia areata. Other types of hair loss are usually due to external causes.

Is hair loss curable?

Can hair loss be cured? The answer is dependent on the cause.

Hair loss due to certain causes is often reversible when the cause has been treated. If that’s the case, the primary treatment for hair loss will be correcting the underlying condition. This includes:

  • Psychiatric treatment

  • Stress management

  • Changing hairstyles or hair care

  • Antifungal drugs for infections

  • Immunosuppressants such as corticosteroids for autoimmune disorders

  • Stopping any medications causing hair loss

If hair loss is due to male or female pattern hair loss, some hair regrowth is possible through hair regrowth treatments. These include:

If hair loss involves the death of hair follicles, then those hair follicles cannot be recovered. Autoimmune disorders, alopecia areata, skin injury, hair pulling, or severe infections can all damage hair follicles and result in permanent hair loss. Medical treatment options to regrow the hair are limited except for hair transplants. 

RELATED: Does finasteride work for women?

How to prevent hair loss

Some types of hair loss can’t be prevented, though many of us wish it could. However, hair loss is often due to things people do unwittingly, not knowing it may affect their hair. A few tips can help prevent unnecessary hair thinning or hair loss:

  • Avoid hairstyles that pull on the hair, such as braids, cornrows, buns, and ponytails

  • Avoid harsh hairstyling chemicals, including many hair dyes, hair straighteners, and perming chemicals

  • To color or perm hair, go to a professional hair stylist who will use gentle chemicals and techniques

  • Avoid curling irons

  • Use a gentle brush

  • Don’t overbrush

  • Wear a hat to avoid getting a sunburn on the scalp

  • Go easy on scratching the head

  • Don’t play with your hair

  • Don’t pull your hair

  • Manage stress and take time to relax

  • Eat a healthy diet

  • Avoid vitamin deficiencies by taking supplements such as iron, biotin, riboflavin, folate, vitamin B12, and vitamin D

  • Avoid taking too much vitamin A

  • Avoid rapid weight loss or crash dieting

Most importantly, see a doctor if hair loss is sudden or unexplainable

For some people, hair loss is genetic. For others, hair loss may be due to something else. It may be diet, lifestyle, infection, or prescribed drugs. If hair starts thinning or falling out for no reason—particularly hair not on the head—see a doctor or other healthcare professional. There may be a more serious underlying condition that needs treatment. Even if there isn’t, hair loss can be upsetting. A healthcare provider or dermatologist may have medical advice or even treatments to help arrest or reverse hair loss.

FAQs about hair loss causes

What blood test is done for hair loss?

Clinicians usually don’t require blood tests to diagnose hair loss unless they suspect it’s due to an underlying medical condition like hypothyroidism, hormone imbalances, nutrient deficiencies, or an autoimmune disorder like alopecia areata.

Can low vitamin D cause hair loss?

Vitamin D deficiency has been associated with hair thinning, particularly male pattern hair loss, stress-induced hair loss (telogen effluvium), and alopecia areata. Vitamin D is important because it stimulates hair follicles to renew themselves and start growing hair after a resting phase.

What hormone imbalance causes hair loss?

Both male pattern and female pattern hair loss are due to testosterone sensitivity. After menopause, the drop in female hormones triggers a rise in male hormones. This hormone imbalance contributes to the gradual thinning of hair in postmenopausal women. Falling estrogen levels after childbirth is another hormone imbalance that causes sudden and rapid hair shedding. Polycystic ovarian syndrome (PCOS) contributes to hair loss in some people. Finally, hormonal birth control, such as birth control pills or Depo-Provera shots, can sometimes cause hair thinning.

What’s next? Additional resources for people with hair loss

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Anne Jacobson, MD, MPH
Board-Certified Family Physician

Anne Jacobson, MD, MPH, is a board-certified family physician, writer, editor, teacher, and consultant. She is a graduate of University of Wisconsin School of Medicine and Public Health, and trained at West Suburban Family Medicine in Oak Park, Illinois. She later completed a fellowship in community medicine at PCC Community Wellness and a master's in Public Health at the University of Illinois-Chicago. She lives with her family near Chicago.

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