Hair Loss

Hair loss (medically called alopecia) is the partial or complete loss of hair from areas where it normally grows, most often the scalp. It ranges from gradual, patterned thinning to sudden, diffuse shedding, and it can be temporary or permanent depending on the underlying cause.

What is hair loss?

Hair loss is not a single disease but a sign shared by many different conditions. To understand it, it helps to understand the hair growth cycle. Each follicle moves through three phases: anagen (active growth, lasting years), catagen (a brief transition), and telogen (resting, after which the hair is shed). At any moment, roughly 85–90% of scalp follicles are in the growing phase and about 10–15% are resting (NIH/StatPearls). Because of this cycle, losing about 50–100 hairs per day is normal.

Hair loss becomes a medical concern when shedding outpaces regrowth, when follicles miniaturize (produce progressively finer, shorter hairs), or when follicles are destroyed. Dermatologists divide alopecia into two broad groups:

• Non-scarring (non-cicatricial) alopecia — the follicle is preserved and regrowth is possible. This includes the most common forms: androgenetic alopecia, telogen effluvium, and alopecia areata.
• Scarring (cicatricial) alopecia — inflammation permanently destroys the follicle and replaces it with scar tissue, so lost hair does not return. This group is less common but more urgent, because early treatment can preserve remaining hair.

In ICD-10, common forms are coded under L63 (alopecia areata), L64 (androgenetic alopecia), and L65 (other non-scarring hair loss, including telogen effluvium).

What causes hair loss and who is at risk?

The causes differ by type, and identifying the right one drives everything that follows.

Androgenetic alopecia (male- and female-pattern hair loss)

This is by far the most common cause. It is driven by genetic susceptibility and the effect of androgens (particularly dihydrotestosterone, DHT) on genetically sensitive follicles, which gradually miniaturize. Prevalence rises steadily with age—affecting a large majority of men and roughly half of women by age 70 in studied populations (StatPearls). Men typically develop a receding hairline and crown thinning; women more often show diffuse thinning over the crown with a preserved frontal hairline.

Telogen effluvium

A temporary, diffuse shedding that occurs when a physiologic stressor pushes an abnormally large share of follicles into the resting phase at once. Common triggers (DermNet, NIH) include childbirth, major surgery, high fever or severe illness, rapid weight loss or crash dieting, iron deficiency, thyroid disease, and certain medications. Shedding usually begins 2–3 months after the trigger.

Alopecia areata

An autoimmune condition in which the immune system attacks hair follicles, producing smooth, round patches of loss on the scalp or body. It can progress to total scalp loss (alopecia totalis) or whole-body loss (alopecia universalis). It is associated with other autoimmune conditions and a family history of the disorder (NIH/NIAMS).

Other contributors

• Medications and treatments — chemotherapy (anagen effluvium), anticoagulants, some antidepressants, retinoids, beta-blockers, and excess vitamin A.
• Nutritional and hormonal factors — iron deficiency, thyroid disorders, and significant protein or calorie restriction.
• Traction alopecia — repeated tension from tight braids, ponytails, or extensions.
• Scarring alopecias — such as lichen planopilaris, frontal fibrosing alopecia, and central centrifugal cicatricial alopecia.
• Fungal infection (tinea capitis) — a common cause of patchy loss in children.

What are the symptoms of hair loss?

Symptoms depend on the cause, and the *pattern* is often the most useful clue:

• Gradual thinning on the top of the head — the hallmark of androgenetic alopecia; a widening part in women, a receding hairline or crown in men.
• Sudden, diffuse shedding — handfuls of hair on the pillow, in the shower, or in the brush, typical of telogen effluvium.
• Circular or patchy bald spots — smooth, coin-sized patches suggest alopecia areata; scaly, itchy, or broken-hair patches suggest infection.
• Full-body hair loss — seen with chemotherapy and severe alopecia areata.
• Redness, scaling, pain, itching, or pustules — these inflammatory signs can point to a scarring alopecia or infection and warrant prompt evaluation.

Warning signs of *scarring* loss include loss of the visible follicle openings (a smooth, shiny scalp), persistent burning or tenderness, and an irregular, advancing border.

How is hair loss diagnosed?

Diagnosis begins with history and a close scalp examination. A clinician typically asks about timing, family history, recent illness or stressors, diet, medications, and hairstyling practices. Several in-office tests refine the picture:

• Hair pull test — the clinician grasps roughly 40–60 hairs and gently pulls; the number that come away helps gauge active shedding, as in telogen effluvium or active alopecia areata. Traditional teaching called extraction of more than about 10% abnormal, but an evidence-based revision proposed a lower normal cutoff (about 2 hairs or fewer) and found the older multi-day restriction on pre-test hair washing can be relaxed (McDonald KA, et al., *J Am Acad Dermatol*. 2017;76(3):472–477, PMID 28010890).
• Dermoscopy (trichoscopy) — magnified inspection of the scalp shows characteristic patterns: follicle miniaturization and variation in hair shaft diameter in androgenetic alopecia; "exclamation-mark" hairs and yellow dots in alopecia areata; loss of follicular openings in scarring types.
• Scalp biopsy — reserved for uncertain cases, suspected scarring alopecia, or non-responding loss; it distinguishes scarring from non-scarring disease.
• Laboratory tests — there is no single blood test for hair loss, but targeted labs help when an internal cause is suspected: ferritin and a complete blood count (iron status), thyroid-stimulating hormone (TSH), and, in women with signs of androgen excess, hormonal studies. A serial daily hair count (collecting shed hairs over 24 hours, with totals at or above ~100 supporting telogen effluvium) can document the degree of shedding.

Severity in androgenetic alopecia is often staged with the Hamilton-Norwood scale (men) or the Ludwig scale (women).

How is hair loss treated?

Treatment depends entirely on the cause, and the most important first step is an accurate diagnosis. The general approach moves from addressing reversible factors, to over-the-counter therapy, to prescription options.

Address the underlying cause and lifestyle factors first

Some hair loss resolves once the trigger is removed. Telogen effluvium is usually self-limited and regrows over 3–6 months once the precipitating illness, deficiency, or medication is corrected. Practical steps include treating iron deficiency or thyroid disease, ensuring adequate protein and overall nutrition, reviewing medications with a prescriber, and easing high-tension hairstyles to prevent traction alopecia. Gentle hair handling does not regrow hair on its own but limits avoidable breakage.

Over-the-counter options

• Topical minoxidil — the only FDA-approved over-the-counter treatment for pattern hair loss, available as a 2% or 5% solution or foam. It prolongs the growth phase and can slow loss and partially regrow hair, but benefit requires continuous use; stopping reverses gains over several months. Temporary increased shedding in the first weeks is common.
• Nutritional correction — supplementation helps only when a documented deficiency (such as low iron) exists; routine supplements do not benefit people with normal nutrient levels.

Prescription and procedural options

• Oral finasteride — a 5-alpha-reductase inhibitor that lowers DHT, slowing loss and modestly regrowing hair in men with androgenetic alopecia. It is not approved for and is generally avoided in women of childbearing potential because of risk to a male fetus. Dutasteride, in the same drug class, is used off-label.
• Low-dose oral minoxidil — increasingly prescribed off-label for several forms of hair loss, with efficacy comparable to the topical form and often better adherence; it requires clinician monitoring for side effects such as fluid retention and unwanted body-hair growth.
• Anti-androgen therapy in women — agents such as spironolactone are used off-label for female-pattern hair loss, often alongside minoxidil.
• Corticosteroids for alopecia areata — intralesional steroid injections for limited patches, with topical or systemic steroids in selected cases.
• Oral JAK inhibitors for severe alopecia areata — a major recent advance. Baricitinib (FDA-approved 2022) and ritlecitinib (FDA-approved 2023) are approved for severe disease, with deuruxolitinib approved in 2024; trials show substantial scalp regrowth in a meaningful share of patients, though continued use is generally needed to maintain results.
• Procedures — platelet-rich plasma (PRP) injections and low-level laser therapy are used as adjuncts with mixed evidence; hair transplantation can restore density in stable pattern loss and is often recommended when medical therapy has not stabilized loss after about a year.

Can hair loss be prevented or managed long-term?

Not all hair loss is preventable—androgenetic alopecia and alopecia areata are driven by genetics and immune factors that cannot be willed away. But several measures genuinely help:

• Treat reversible causes early. Correcting iron deficiency, thyroid disorders, or a triggering medication can halt and reverse shedding.
• Start pattern-hair-loss therapy sooner rather than later. Minoxidil and finasteride are better at preserving existing follicles than regrowing long-dormant ones, so earlier treatment generally yields better long-term retention.
• Protect against avoidable damage. Limit chronic tension hairstyles, harsh chemical processing, and high-heat styling to prevent traction alopecia and breakage.
• Set realistic expectations. For chronic conditions, treatment is ongoing maintenance; benefits typically fade if therapy stops.

When should you see a doctor?

Most hair shedding is benign, but certain features deserve professional evaluation:

• Sudden, rapid, or patchy hair loss rather than gradual thinning.
• Scalp redness, scaling, pain, burning, itching, or pustules, or a smooth, shiny scalp where follicle openings have disappeared—possible signs of scarring alopecia or infection that can cause permanent loss.
• Hair loss with other symptoms such as unexplained fatigue, weight change, or menstrual irregularities, which may signal a thyroid, hormonal, or nutritional disorder.
• Hair loss after starting a new medication, to discuss alternatives.
• Significant distress about appearance, regardless of the amount—effective treatments exist, and early care improves outcomes.

Scarring alopecias in particular are time-sensitive: once a follicle is destroyed, the loss is permanent, so early diagnosis is critical.

What is the outlook (prognosis)?

The outlook depends heavily on the type. Telogen effluvium is usually fully reversible, with regrowth over several months once the trigger resolves. Androgenetic alopecia is progressive without treatment, but therapy can slow or partly reverse it and is most effective when started early; results require ongoing maintenance. Alopecia areata is unpredictable—many people with limited patches regrow hair spontaneously, while extensive disease is harder to treat, though JAK inhibitors have meaningfully improved options for severe cases. Scarring alopecias carry the most guarded prognosis because destroyed follicles cannot regrow, making early intervention essential to preserve remaining hair. Across all types, hair loss is not life-threatening, and its substantial psychological impact is well recognized and treatable.

Frequently asked questions

Is it normal to lose hair every day? Yes. Shedding roughly 50–100 hairs per day is a normal part of the hair cycle. Concern is warranted when you notice a clear increase, visible thinning or bald patches, or hair not regrowing.

Will my hair grow back? It depends on the cause. Telogen effluvium and many cases of alopecia areata regrow. Androgenetic alopecia can be slowed and partly reversed with treatment but tends to progress if untreated. Scarring alopecias generally do not regrow, which is why early evaluation matters.

Do over-the-counter supplements and "hair growth" vitamins work? They help only if you have a true deficiency, such as low iron. In people with normal nutrient levels, evidence that general supplements regrow hair is weak, and excess of some nutrients (for example, vitamin A or selenium) can actually cause hair loss.

Does stress cause hair loss? Severe physical or emotional stress can trigger telogen effluvium, a temporary diffuse shedding that begins a couple of months after the event. It typically reverses once the stressor passes. Stress is not the cause of androgenetic alopecia.

How long until I see results from treatment? Hair grows slowly, so most therapies require 3–6 months of consistent use before noticeable change, and ongoing use to maintain it. Some people experience a brief increase in shedding when starting minoxidil before improvement appears.