Hair Loss: Causes, Types, Treatment & When to See a Doctor

Written by Dima Bader, DDS

Medically reviewed by Swathi Kilari MD

Last reviewed October 2, 2026

Hair loss, medically called alopecia, is excessive shedding or thinning of hair. It can result from genetics, hormonal changes, medical conditions, stress, medications, nutritional problems, or damage from certain hairstyles and hair treatments. Some forms are temporary, while others are permanent.

It can affect the scalp or other parts of the body, and the pattern, whether gradual thinning, a receding hairline, or sudden patchy loss, often points toward a specific cause. Identifying which type you have is the first step toward finding a treatment that works.

What Is Hair Loss?

Hair loss happens when hair falls out faster than the body replaces it, or when a hair follicle stops producing new hair. It can show up as thinning across the scalp, a widening part, a receding hairline, distinct bald patches, or, in more extensive cases, loss of most or all scalp and body hair. Some types resolve once an underlying trigger passes, while others progress steadily or permanently damage the follicle.

Is It Normal to Lose Hair Every Day?

Yes. According to the American Academy of Dermatology (AAD), losing about 50 to 100 hairs a day is a normal part of the hair growth cycle. Each follicle cycles through phases of growth, rest, and shedding on its own schedule, so some daily shedding simply reflects old hairs making room for new ones.

When Does Hair Shedding Become Hair Loss?

Shedding becomes a concern when hair isn’t being replaced at the same rate, or when you notice visible changes: clumps of hair in the shower drain or on your pillow, a more visible scalp, a hairline that has moved, or patches where hair has disappeared. If thinning, bald spots, or unusually heavy shedding persist for more than a few weeks, it’s reasonable to treat it as hair loss rather than normal turnover and have it evaluated. The NHS advises seeing a GP if hair loss is sudden, patchy, or causing distress.

What Causes Hair Loss?

Hair loss has many possible causes, which is why identifying the underlying one matters before choosing a treatment. An approach that works well for genetic thinning may do nothing for hair loss caused by stress, and vice versa.

Hereditary Hair Loss

The most common cause of hair loss is androgenetic alopecia, better known as male or female pattern hair loss. It is driven by genetics and sensitivity to androgens (hormones present in both men and women), which gradually shrink hair follicles over time. It tends to progress slowly with age and often runs in families. In men, it typically appears as a receding hairline with thinning at the crown.

In women, it more often appears as a widening part and diffuse thinning across the top of the scalp, usually with the frontal hairline preserved. Mayo Clinic describes hereditary hair loss as by far the most common cause of hair loss.

Hormonal Changes

Hormones regulate the hair growth cycle, so shifts in hormone levels can trigger shedding or thinning. Common hormonal contributors include:

• Pregnancy and the postpartum period (shedding after childbirth is usually a form of telogen effluvium)
• Menopause
• Thyroid disorders, both underactive and overactive
• Starting or stopping hormonal birth control
• Polycystic ovary syndrome (PCOS)

Stress and Physical or Emotional Shock

Significant physical or emotional stress can push a large number of follicles into the shedding phase at once, a pattern called telogen effluvium. The hair loss typically appears two to three months after the triggering event, which is why the connection is easy to miss. According to Mayo Clinic, triggers include high fever, major surgery, significant weight loss, and stressful life events. It is generally temporary and resolves once the trigger passes. If stress is a factor, our guide on how to reduce stress may help.

Nutritional Deficiencies

Hair follicles are sensitive to nutrient shortfalls. Low iron, inadequate protein intake, and very low-calorie diets have all been associated with increased shedding, although the evidence for individual nutrients is mixed. Supplements aren’t automatically the fix, and the AAD notes that getting too much of certain nutrients, including selenium, vitamin A, and vitamin E, can worsen hair loss. If a deficiency is suspected, confirm it through testing rather than guessing with supplements. A balanced diet with enough protein supports normal hair growth.

Medical Conditions

A number of health conditions can contribute to hair loss, including:

• Thyroid disorders
• Alopecia areata, an autoimmune condition that attacks hair follicles
• Scalp infections, such as ringworm (tinea capitis)
• Certain other autoimmune conditions

Persistent fatigue alongside hair loss is one reason a clinician may check for thyroid or nutritional problems.

Medications and Medical Treatments

Hair loss is a recognized side effect of several medications, including some used for cancer, arthritis, depression, heart conditions, gout, and high blood pressure. Chemotherapy is a well-known cause of rapid, widespread hair loss (anagen effluvium) because it affects hair while it is actively growing. Radiation therapy to the head can also cause hair loss in the treated area. Never stop a prescribed medication without speaking to your prescriber.

Hairstyles and Hair Treatments

Repeated tension from tight ponytails, braids, cornrows, extensions, or weaves can damage follicles over time, a condition called traction alopecia. According to the AAD, hairstyles that pull can lead to permanent hair loss if the tension continues long enough to damage the follicle, although early stages are often reversible. Frequent chemical relaxers, perms, and heat styling can damage the hair shaft and cause breakage.

What Are the Different Types of Hair Loss?

Pattern Hair Loss

Androgenetic alopecia doesn’t look identical in everyone. The classic presentations, a receding hairline and crown thinning in men and diffuse thinning with an intact frontal hairline in women, are common but not universal, and some people have a mix of patterns. It usually progresses gradually over years. The NHS and NICE guidance both describe it as the most common type.

Telogen Effluvium

This type causes diffuse shedding across the whole scalp rather than isolated patches. It is usually triggered by illness, major stress, childbirth, or substantial weight loss, and it typically resolves within several months once the trigger has passed, although some people experience a longer (chronic) course. If shedding followed weight loss, restoring adequate nutrition is part of recovery.

Alopecia Areata

Alopecia areata is an immune-related condition in which the body mistakenly attacks its own hair follicles, usually producing round or oval patches of hair loss. According to the AAD, many people, especially children with limited patches, regrow hair without treatment, but the course is unpredictable and new patches can appear later. The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) provides further background.

Traction Alopecia

Traction alopecia develops where hair is repeatedly pulled tight, most often along the hairline or part. Caught early, it is usually reversible once the tension stops. Left unaddressed for years, it can progress to permanent follicle damage.

Scarring Hair Loss

Scarring (cicatricial) alopecias cause permanent damage because the follicle is destroyed and replaced by scar tissue. Examples include central centrifugal cicatricial alopecia, which often starts at the crown and spreads outward, and frontal fibrosing alopecia, which causes a receding hairline, often with eyebrow loss. Because a destroyed follicle cannot regrow hair, early evaluation by a dermatologist is especially important, as treatment aims to stop further loss.

What Are the Signs and Symptoms of Hair Loss?

Hair loss doesn’t look the same for everyone. Common signs include:

• Gradual thinning on the top of the head
• A widening part
• A receding hairline
• Distinct bald spots or patches
• Sudden, noticeable shedding
• Broken hairs of varying lengths
• Loss of eyebrows or eyelashes
• Scalp scaling, redness, itching, or pain
• Shiny, smooth patches of scalp where follicles may have been destroyed

According to Mayo Clinic, hair loss can develop gradually or suddenly and, depending on the cause, may be limited to the scalp or affect the whole body.

Hair Loss vs. Hair Breakage

Hair loss happens at the follicle, meaning the hair falls out from the root. Breakage happens along the hair shaft, often from heat styling, chemical treatments, or rough handling, and the hair snaps rather than shedding from the root. Breakage usually responds to gentler hair care, while true hair loss often requires addressing the underlying cause.

How Is Hair Loss Diagnosed?

Self-diagnosis can be difficult because very different conditions can look similar. A dermatologist typically combines several pieces of information.

Medical History

A clinician will usually ask about:

• Family history of hair loss
• Recent illness or surgery
• Stress levels
• Weight changes
• Diet
• Medications
• Pregnancy or other hormonal changes
• Hair-care practices and styling habits

Scalp and Hair Examination

A dermatologist examines the scalp and the pattern of loss directly, sometimes using magnification or dermoscopy to look closely at follicles and hair shafts.

Blood Tests

Depending on the suspected cause, blood tests may help identify an underlying condition, such as a thyroid disorder, or a nutritional deficiency, such as low iron.

Hair Pull Test or Other Tests

According to Mayo Clinic, a doctor may also use a pull test (gently tugging a small group of hairs to see how many come out), a scalp biopsy to examine hair roots, or light microscopy to look for abnormalities in the hair shaft. Fungal scalp infections are diagnosed with a scalp scraping or culture.

How Is Hair Loss Treated?

Treatment depends heavily on the cause, and no single approach works for every type.

Minoxidil

Topical minoxidil, sold over the counter under brand names such as Rogaine, is FDA-approved for pattern hair loss in men and women. According to the AAD, it can help with early hair loss but cannot regrow an entire head of hair, and it tends to work best when paired with another treatment. Results usually take at least several months, benefits fade if treatment stops, and some people notice temporary extra shedding at the start. Discuss possible side effects with a healthcare provider.

Prescription Medications

Depending on the cause, a dermatologist may consider options such as:

• Finasteride, an oral medication for pattern hair loss in men. Possible side effects, including sexual and mood-related symptoms, should be discussed with a clinician, and it is not appropriate for people who are or may become pregnant.
• Corticosteroid injections, topical immunotherapy, or JAK inhibitors for some cases of alopecia areata, with FDA-approved oral JAK inhibitors available for severe disease
• Oral antifungal medication for tinea capitis
• Other condition-specific medications tailored to the underlying cause

Dosing and candidacy should be individualized by a qualified clinician rather than self-prescribed.

Treatment for Underlying Medical Conditions

When hair loss stems from a condition such as a thyroid disorder or iron deficiency, treating that condition is often what allows hair to regrow. Correcting the root cause tends to be more effective than treating the hair loss alone.

Hair Transplantation

Hair transplant surgery moves follicles from a donor area to thinning or balding areas. It is generally considered for selected people with stable, long-term pattern hair loss, typically after other options have been explored.

Low-Level Laser Therapy

Some low-level laser devices are FDA-cleared for pattern hair loss, but the strength of the evidence varies by device and cause. Ask a provider whether it makes sense for your situation.

Platelet-Rich Plasma (PRP)

PRP involves drawing a small sample of your own blood, concentrating the platelets, and injecting them into the scalp. It usually requires several sessions, protocols are not standardized, and results vary from person to person. Evidence for its effectiveness is still developing.

Treatment for Alopecia Areata

Treatment depends on how much hair has been lost and for how long. According to the AAD, options include corticosteroid injections, topical treatments, and newer oral medications for more extensive cases, and many people with limited patches regrow hair without treatment.

Can Hair Loss Be Prevented?

Genetically driven hair loss can’t be fully prevented, but a meaningful amount of avoidable hair damage can be reduced with the right habits.

Avoid Tight Hairstyles

Repeated tension from tight ponytails, braids, cornrows, or extensions is one of the more avoidable contributors to hair loss. According to the AAD, a hairstyle that causes pain or discomfort is likely too tight and worth loosening or changing before it causes lasting damage.

Be Gentle With Hair

The AAD recommends gentle hair care for anyone noticing thinning, including:

• Brushing gently rather than tugging through tangles
• Using conditioner to reduce friction and breakage
• Limiting heat styling
• Avoiding aggressive chemical treatments when possible

Maintain a Balanced Diet

Adequate nutrition supports healthy hair growth, but more is not automatically better. As noted above, excessive amounts of some nutrients can worsen hair loss, so approach supplements thoughtfully. Our guide to a healthy diet is a good starting point.

Address Underlying Health Problems

If hair loss is persistent or unexplained, a medical evaluation is generally more productive than trying product after product. Identifying and treating a hormonal, nutritional, or autoimmune issue gives hair the best chance of recovering.

When Should You See a Doctor About Hair Loss?

Most people shed some hair every day without it signaling a problem. These patterns are worth having evaluated by a doctor or dermatologist:

• Sudden or rapid hair loss
• Severe or widespread shedding
• Hair loss in clearly defined patches
• Scalp pain, redness, scaling, or inflammation
• Loss affecting the eyebrows or eyelashes
• Hair loss with other unexplained symptoms, such as fatigue or weight changes
• Hair loss after significant weight loss or recent illness
• Visible scarring where hair has been lost
• Hair loss that persists without an obvious explanation
• Hair loss that is causing significant emotional distress

The AAD recommends seeing a dermatologist because hair loss has so many possible causes, and early diagnosis generally improves treatment options, particularly for scarring alopecias where delay can mean permanent follicle loss.

Common Myths About Hair Loss

Does Shampoo Cause Hair Loss?

No. Washing your hair doesn’t make it fall out faster. Hairs that come out in the shower were already in the shedding phase.

Does Wearing a Hat Cause Hair Loss?

No. Ordinary hat or helmet use isn’t considered a cause of pattern hair loss, which has a genetic and hormonal basis.

Does Cutting Your Hair Make It Grow Back Thicker?

No. Trimming the hair shaft has no effect on the follicle beneath the scalp, which determines thickness and growth rate.

Does Hair Loss Always Mean You Are Sick?

No. Genetic and age-related hair loss are extremely common and don’t indicate an underlying illness. However, sudden, patchy, or unexplained hair loss can sometimes point to a medical condition, so unusual patterns are worth checking.

Do Hair Growth Supplements Always Work?

No. Supplements aren’t universally effective, and the AAD notes that excessive amounts of certain nutrients can worsen hair loss. If a deficiency is confirmed through testing, correcting it can help, but supplementing without a known deficiency isn’t a reliable fix.

Frequently Asked Questions About Hair Loss

What causes hair loss?
Genetics (pattern hair loss), hormonal changes, medical conditions, stress, nutritional deficiencies, certain medications, scalp infections, and hairstyling habits that put tension on the hair.

Is it normal to lose hair every day?
Yes. Losing roughly 50 to 100 hairs a day is a normal part of the hair growth cycle.

Why is my hair suddenly falling out?
Sudden shedding is often linked to a stressful event, illness, major weight loss, childbirth, or a medication change, typically appearing two to three months after the trigger. This pattern, telogen effluvium, is usually temporary. See a doctor if shedding is severe, patchy, or doesn’t settle.

Can stress cause hair loss?
Yes. Significant physical or emotional stress can push follicles into a shedding phase, causing temporary but sometimes substantial hair loss.

Can hormonal changes cause hair loss?
Yes. Pregnancy, childbirth, menopause, thyroid disorders, PCOS, and changes in hormonal birth control can all trigger thinning or shedding.

Can hair grow back after hair loss?
It depends on the type. Non-scarring types, such as telogen effluvium and traction alopecia caught early, often regrow once the cause is removed. Alopecia areata is also non-scarring and often regrows, though the course is unpredictable. Scarring types permanently destroy the follicle, so hair in those areas typically doesn’t return.

What vitamin deficiency causes hair loss?
Iron deficiency is one of the more commonly discussed nutritional causes, and inadequate protein or very low-calorie diets can also contribute. Testing is the best way to confirm a deficiency before starting supplements.

Does minoxidil work for hair loss?
Topical minoxidil is FDA-approved for pattern hair loss in men and women and can help with early hair loss, but it generally cannot regrow an entire head of hair and works best alongside another treatment.

Can hair loss be prevented?
Hereditary hair loss can’t be fully prevented, but avoiding tight hairstyles, using gentle hair care, maintaining good nutrition, and treating underlying conditions can reduce avoidable damage.

Is hair loss permanent?
Not always. Telogen effluvium and many cases of alopecia areata are temporary. Scarring alopecias cause permanent follicle damage, and pattern hair loss tends to progress without treatment.

When should I see a doctor for hair loss?
See a doctor if hair loss is sudden, patchy, or widespread, comes with scalp redness or scaling, affects your eyebrows or eyelashes, or occurs alongside other unexplained symptoms.

Key Takeaways

• Losing some hair every day is normal; a change in pattern, rate, or appearance signals true hair loss.
• Causes include genetics, hormonal changes, medical conditions, stress, medications, and hair-care practices.
• Different types need different treatments, so an accurate diagnosis matters more than guessing at a fix.
• Early evaluation is especially important when hair loss is sudden, patchy, painful, or accompanied by scalp changes, because some types cause permanent follicle damage.
• Gentle hair care can reduce avoidable damage from styling and tension.
• Treatments typically take months, not days, to show visible results.
• A dermatologist can identify the underlying cause and recommend suitable treatment.

Sources

• American Academy of Dermatology: Hair loss, Hairstyles that pull, Alopecia areata, Minoxidil, Tips for managing hair loss
• Mayo Clinic: Hair loss: Symptoms & causes, Hair loss: Diagnosis & treatment
• NHS: Hair loss
• NICE CKS: Alopecia, androgenetic
• NIAMS: Alopecia areata

Medical Disclaimer

This article is for general information and education. It is not medical advice and cannot diagnose the cause of your hair loss. Sudden, patchy, or progressive hair loss, or hair loss accompanied by other symptoms, should be evaluated by a qualified dermatologist or healthcare provider.

Read our full Medical Disclaimer.