Hairline Journal

PRP and Low-Level Laser Therapy for Hair Loss: What the Evidence Shows

2026-11-08T00:00:00Z

Platelet-rich plasma (PRP) injections and low-level laser therapy (LLLT) are two procedures often considered for pattern hair loss alongside medication. Both have been tested in randomized trials, and both come with real gaps in the evidence. The American Academy of Dermatology (AAD) groups at-home laser devices and PRP among emerging or limited-evidence options, and DermNet describes PRP as under investigation and the benefit of LLLT as unproven. This guide looks at what the trials actually show, what FDA clearance means for laser devices, how treatment is usually scheduled and where the limits are.

Platelet-rich plasma

How PRP is prepared

A 2022 review in Drug Design, Development and Therapy describes the process. A small amount of the patient's own blood, roughly 10 to 60 mL, is drawn into tubes containing an anticoagulant and spun in a centrifuge. This separates the blood into layers, and the platelet-rich middle layer is collected and injected into the scalp. The platelet concentration is typically two to six times the normal level in blood.

There is no standard method. The review notes that commercial kits differ in platelet concentration, white blood cell content and whether an activator is added, and there is no agreement on whether activation helps.

What the trials show

A 2023 meta-analysis in Aesthetic Plastic Surgery pooled 10 randomized trials with 318 participants that compared PRP with saline injections in androgenetic alopecia. Its main findings:

Hair density: PRP increased density by an average of about 25 hairs per square centimetre compared with saline.
Hair thickness: no significant difference in hair diameter.
Who benefited most: trials that enrolled only men showed larger effects than mixed trials, and smaller trials showed larger effects than bigger ones. The authors caution that small studies can overestimate benefit.
Follow-up: the included trials ran for 3 to 6 months, and none assessed results beyond 12 months.

For women, the 2022 review reports mixed findings. One women-specific meta-analysis found that PRP increased hair diameter but not density, and the review notes that evidence on whether sex affects the response is still debated.

Sessions and scheduling

Protocols vary widely between studies. The 2022 review lists these as common regimens:

Monthly injections for three to four sessions, the pattern used in most trials
Sessions every two to three weeks, for example four sessions spaced 15 days apart
Weekly sessions, used in one trial in women

One proposed protocol uses monthly sessions for three months, then a session every three months for the first year. No standard maintenance schedule has been established.

Side effects and who should avoid it

The review describes side effects as generally mild and temporary: pain during the injections, mild headache, minimal itching, and short-lived redness and swelling at the injection sites. No major complications were reported in the studies it reviewed.

It lists these as reasons not to have PRP:

Absolute: very low platelet count, platelet function disorders, unstable circulation, sepsis or infection at the treatment site
Relative: anti-inflammatory painkiller (NSAID) use within 48 hours, recent steroid injections at the site or recent oral steroids, a recent illness or fever, cancer, anaemia, a low platelet count and tobacco use

Regulatory status

The 2022 review explains that both the devices used to separate platelets and the PRP product fall under FDA regulation, and that using PRP for anything other than transfusion is off-label. Off-label use is permitted when a physician uses it as part of medical practice. The review lists oral finasteride for men and topical minoxidil as the FDA-approved hair loss treatments, and PRP is not among them.

Low-level laser therapy

What the devices are

LLLT devices shine low-power red light onto the scalp. A 2021 systematic review in the Journal of Clinical and Aesthetic Dermatology found 32 home-use devices marketed in the US as of January 2020, in four designs: caps, helmets, combs and headbands. Most used laser diodes, and most emitted light between 620 and 678 nm, typically around 650 to 655 nm.

The power involved is low: one device described in an FDA filing uses diodes rated below 5 mW each. Lasers used to resurface skin are a different group of devices.

What FDA clearance means

Home laser devices for hair loss are cleared through the FDA's 510(k) pathway. The clearance letter for one such device (K222477, issued in November 2022) shows how this works:

Regulation: 21 CFR 890.5500, regulation name "Infrared Lamp", Class II, product code OAP ("Laser, Comb, Hair")
Basis: the FDA found the device "substantially equivalent" to devices already legally on the market
Indication: to promote hair growth in men with androgenetic alopecia at Hamilton-Norwood stages IIa to V and women at Ludwig-Savin stages I to II, with Fitzpatrick skin types I to IV, sold over the counter
Testing submitted: the summary lists non-clinical testing, such as biocompatibility and electrical safety

So "FDA-cleared" means the agency accepted that a device is similar enough to an earlier one. It is a different standard from FDA approval of a drug. The letter also notes that a substantial equivalence determination does not mean the FDA has found the device compliant with every other legal requirement.

What the trials show

The 2021 review pooled seven double-blind, sham-controlled trials with 607 participants. Devices increased hair density more than sham devices, with similar effects in men and women. Devices using only laser diodes showed a larger effect than those combining lasers with LEDs.

Sessions

Most devices in the review were used three to four times a week, with sessions lasting from 90 seconds to 36 minutes, a median of 30 minutes. One device was used daily.

Side effects

Reported side effects were generally mild, including tingling, hives, headache, dry skin, itching and scalp tenderness. Some trials reported none.

How the two compare

	PRP	Low-level laser therapy
Where it is done	In a clinic, by injection	Mostly at home, with a cap, helmet, comb or headband
Typical schedule	Often monthly for 3 to 4 sessions, protocols vary	Usually 3 to 4 times a week
FDA status	Off-label; PRP is not an FDA-approved hair loss treatment	Devices cleared through 510(k) as substantially equivalent to earlier devices
Main trial finding	Higher hair density than saline; no clear change in hair thickness	Higher hair density than sham devices
Longest trial follow-up	No assessment beyond 12 months	No trial longer than 26 weeks
Common side effects	Injection pain, redness, swelling, mild headache	Mild tingling, itching, scalp tenderness

The limits of the evidence

For PRP, the meta-analysis found substantial variation between trials, linked to small sample sizes, sex, hair loss stage and differing preparation methods, and too few trials in women. The 2022 review adds that many studies were small, uncontrolled or non-randomized, and that some found PRP ineffective. For LLLT, the 2021 review notes short follow-up, small trials, varied wavelengths and power, no head-to-head device comparisons and data limited to mild to moderate hair loss.

Because the laser trials covered only mild to moderate hair loss, results in more advanced hair loss are unknown. Both treatments are worth discussing with a dermatologist alongside the FDA-approved options, oral finasteride for men and topical minoxidil.

Dandruff vs Seborrheic Dermatitis: Differences, Causes and Medicated Shampoos

2026-10-31T00:00:00Z

Flakes on dark clothing and an itchy scalp are among the most common skin complaints, and the words "dandruff" and "seborrheic dermatitis" are often used as if they meant the same thing. They are closely related. DermNet describes dandruff as a mild, uninflamed form of seborrheic dermatitis on the scalp, and Cleveland Clinic notes that seborrheic dermatitis on a teenager's or adult's scalp is usually just called dandruff. The difference lies mainly in how much inflammation is present and where on the body it appears.

How the two differ

Feature	Dandruff	Seborrheic dermatitis
Where it appears	Scalp	Scalp, eyebrows, sides of the nose, ears, beard, eyelids, chest and skin folds
Scale	Fine, bran-like white flakes	Greasy, white-to-yellow scale, sometimes thick plaques
Redness	No underlying redness	Ill-defined red or salmon-pink patches; on skin of colour, lighter patches may appear instead
Itch	Can be itchy	Itch is usually mild
Care needed	Most people manage it at home with dandruff shampoo (AAD)	Chronic and relapsing in adults, often needing maintenance

These descriptions come from DermNet, Cleveland Clinic and the NHS. DermNet notes that seborrheic dermatitis is sometimes seen together with psoriasis, a combination called sebopsoriasis.

Who gets seborrheic dermatitis

DermNet estimates that it affects about 3% to 12% of people, with two peaks. In babies it shows up as cradle cap, usually in the first three months, and often clears by 6 to 12 months. In adults it is more common in men. Factors linked with it include oily skin, a family history, a weakened immune system, Parkinson's disease and some medicines. Cleveland Clinic adds rosacea, psoriasis and acne to the list of related skin conditions.

What causes it

The role of Malassezia

Malassezia is a yeast that lives on everyone's skin and is usually harmless. Cleveland Clinic explains that when too much of it grows, it triggers a skin reaction. The yeast thrives in oily areas, and it produces a substance that converts skin oil into a fatty acid, which irritates the skin and causes redness, itching and flakes. DermNet describes the same process: enzymes from the yeast break down oils in sebum, which may trigger inflammation.

Yeast alone does not explain the whole picture. A review in the International Journal of Cosmetic Science, written by industry scientists, points out that Malassezia is also found on healthy scalps, so it cannot be the only cause. The two species most common on the scalp are M. globosa and M. restricta. The review lists three contributing factors that act together: the yeast, the amount of scalp oil and individual susceptibility.

A weaker skin barrier

That individual susceptibility appears to involve the outer layer of skin. The same review reports that the scalp in dandruff shows depleted barrier lipids, more water loss through the skin and low-level inflammation. Cleveland Clinic similarly notes that over time the irritation weakens the skin's outer barrier.

What does not cause it

The NHS states that dandruff is not caused by poor hygiene, although flakes may be more obvious when hair is washed less often.

Common triggers

Stress and lack of sleep: DermNet lists both as triggers for flares, and the NHS says stress can make dandruff worse.
Season: flares are typically worse in winter and improve in summer (DermNet). The NHS also mentions cold weather.

The oily scalp connection

Cleveland Clinic notes that Malassezia grows well in oily areas, and DermNet describes seborrheic dermatitis as affecting the parts of the body richest in oil glands, and lists oily skin as a risk factor. The AAD's washing advice reflects this. For fine, straight or oily hair, it suggests washing often, possibly daily, and using a dandruff shampoo about twice a week. For coarse, curly or coily hair, it suggests washing as needed and using a dandruff shampoo about once a week, applied only to the scalp because the active ingredients can dry out hair.

Medicated shampoo ingredients

The AAD lists zinc pyrithione, salicylic acid, sulfur, selenium sulfide, ketoconazole and coal tar as ingredients to look for. The NHS names ketoconazole, coal tar and salicylic acid. DermNet and Cleveland Clinic add ciclopirox, an antifungal available on prescription.

Ingredient	What the sources say
Ketoconazole	Antifungal; Cleveland Clinic lists it as a prescription shampoo, while the NHS and AAD list it among dandruff shampoo ingredients. The cosmetic science review notes greater lasting effect and some anti-inflammatory action
Zinc pyrithione	Antifungal; widely used and able to reach into the hair follicle (cosmetic science review)
Selenium sulfide	Antifungal with cytostatic effects, meaning it slows cell growth (cosmetic science review)
Salicylic acid	Listed by the AAD and NHS as a dandruff shampoo ingredient
Coal tar	Listed by the AAD, NHS, DermNet and Cleveland Clinic
Ciclopirox	Prescription antifungal shampoo (DermNet, Cleveland Clinic)

The cosmetic science review reports that an in-use comparison found no significant difference in antifungal effect between selenium sulfide, zinc pyrithione and ketoconazole, and that no well-controlled study has ranked them definitively.

How to use them

Leave it on: the AAD says some shampoos should stay on the scalp for 5 to 10 minutes before rinsing, and Cleveland Clinic suggests at least five minutes.
Rotate: if one shampoo does not help, the AAD suggests alternating between products with different active ingredients.
Give it time: the NHS suggests using an anti-dandruff shampoo for up to four weeks and trying more than one type if needed.
Keep going: DermNet notes that adult seborrheic dermatitis often needs long-term maintenance, and Cleveland Clinic describes it as a condition that comes and goes.

Prescription options

When shampoos are not enough, DermNet and Cleveland Clinic describe short courses of mild steroid treatments, antifungal creams for the face and body, and calcineurin inhibitor creams for longer-term use on the face. Oral antifungals and light therapy are reserved for resistant cases.

When to see a doctor

The NHS recommends a non-urgent GP visit if symptoms continue after at least four weeks of anti-dandruff shampoo, if dandruff is severe or very itchy, if the scalp is red or swollen, or if flaky, itchy patches appear on the face or body. The AAD adds that a dermatologist can check whether flaking is a sign of another condition, such as psoriasis, a scalp fungal infection or eczema.

Telogen Effluvium: Hair Shedding After Illness, Stress, Childbirth or Diet

2026-10-23T00:00:00Z

Finding clumps of hair in the shower drain a few months after a bad flu, a hospital stay or the birth of a baby is alarming. A common explanation is telogen effluvium, a temporary form of shedding. DermNet describes it as a non-scarring, diffuse hair loss that follows a shock to the body, with new hair continuing to grow underneath. This guide covers why it happens, how long it usually lasts, when hair comes back and what a doctor may check.

What happens in the hair cycle

Each scalp hair goes through a growing phase (anagen) and a resting phase (telogen), after which it falls out and is replaced. DermNet explains that normally about 85% of scalp follicles are in the growing phase and about 15% are resting. After a trigger, a large share of growing hairs can switch into the resting phase at the same time. Those hairs then fall out together a few months later, which is why the shedding seems to arrive long after the event that caused it.

Some daily shedding is normal. The AAD and the NHS both put normal loss at 50 to 100 hairs a day. Cleveland Clinic notes that people with telogen effluvium can lose up to 300 hairs a day.

Common triggers

The AAD, DermNet and Cleveland Clinic list similar triggers:

Illness: high fever, severe infection or recovery from a serious illness
Childbirth: shedding after pregnancy is one of the most familiar forms
Surgery or injury: major operations and accidents
Psychological stress: a period of intense emotional strain
Diet and weight loss: the AAD mentions losing 20 pounds or more, and Cleveland Clinic mentions fad diets that lack protein; DermNet adds nutritional deficiency such as low iron
Thyroid disorders: both underactive and overactive thyroid
Stopping the contraceptive pill
Some medicines: Cleveland Clinic names retinoids, beta-blockers, calcium channel blockers, antidepressants and NSAIDs

The Indian expert consensus in the International Journal of Trichology notes that no trigger can be found in nearly one-third of cases.

Timeline: when it starts and when it stops

The delay between trigger and shedding is the most useful clue. The sources agree on a broadly similar pattern.

Stage	Typical timing	Source
Shedding begins	About 2 to 4 months after the trigger	DermNet; Cleveland Clinic gives 2 to 3 months
After childbirth	Starts around 2 months, peaks around 4 months	AAD
Active shedding	Usually 3 to 6 months	Cleveland Clinic
Back to normal fullness	Usually 6 to 9 months	AAD; DermNet
Chronic form	Shedding lasting more than 6 months	Cleveland Clinic; expert consensus

The AAD adds that shedding can last longer if the stressor continues, especially with ongoing chronic stress. The expert consensus notes that shedding may continue, to a lesser degree, for up to six months after the trigger is removed, and that significant regrowth can take more than a year.

Acute and chronic telogen effluvium

Cleveland Clinic separates acute cases, which last fewer than six months, from chronic cases, which last longer, affect the whole scalp and may have no clear cause. Chronic telogen effluvium is more likely in women aged 30 to 60. Cleveland Clinic reports that about 95% of acute cases resolve.

How it looks

DermNet and Cleveland Clinic describe:

Thinning spread across the whole scalp, often most visible on top, with no complete bald patches
More hair than usual in brushes, drains and on pillows
Short, fine new hairs along the hairline as regrowth begins
A healthy-looking scalp

That last point matters. Cleveland Clinic notes that the scalp in telogen effluvium is usually free of rash, itching, burning, pain and flaking. If the scalp is red, itchy or flaky, another condition may be involved.

How doctors diagnose it

Diagnosis is usually clinical. Cleveland Clinic describes a scalp exam and a pull test, in which a clinician gently tugs a group of 40 to 60 hairs. If four to six hairs come out with white bulbs at the roots, that points to telogen effluvium. The clinician will also ask about diet, medicines and any illness or stress about three months before the shedding started. DermNet adds that a trichogram, a closer look at plucked hairs, showing more than 25% resting hairs strongly suggests the condition. A scalp biopsy is rarely needed.

Blood tests a doctor may order

Practice varies, and the evidence is mixed.

The expert consensus recommends a basic set for anyone with diffuse hair loss: a complete blood count, a urine test, vitamin D and thyroid function. It lists further tests for when the history points to a specific problem, including iron studies with ferritin, vitamin B12, zinc, calcium, serum proteins and hormone tests.
Cleveland Clinic says testing is usually unnecessary and that blood tests or a biopsy are recommended when a provider suspects an underlying condition.
A 2026 analysis in JAAD International compared 26 blood tests in more than 13,000 women with telogen effluvium against matched controls and found that no test helped identify the cause. The authors suggest testing when there are specific symptoms, such as thyroid concerns or weight change, and discourage routine testing when the rest of the health review is normal.

Taken together, these sources point toward tests chosen to match a person's symptoms and history.

Treatment and recovery

There is no single treatment because telogen effluvium is a reaction to something else. DermNet and Cleveland Clinic focus on finding and addressing the cause, whether that is a thyroid problem, a nutritional gap or a medicine. The expert consensus suggests changing a suspected drug for at least three months, with a doctor's guidance.

Other measures from these sources:

Gentle handling: DermNet advises avoiding vigorous combing, brushing and scalp massage while shedding is active.
Diet: a nutritious diet with enough protein, fruit and vegetables.
Minoxidil: Cleveland Clinic lists over-the-counter minoxidil as an option, while noting it should be avoided during pregnancy or breastfeeding.
Camouflage: hairstyles, wigs or hair weaves while hair regrows.

The outlook is good. Cleveland Clinic says hair usually regrows without treatment, and the NHS notes that hair loss caused by a medical condition usually stops or grows back once the condition is treated. DermNet adds two caveats: recovery may be incomplete, and repeated episodes can sometimes develop into female pattern hair loss.

When to see a doctor

The AAD recommends seeing a dermatologist if you are worried about how much hair you are losing, since some people have shedding and another type of hair loss at the same time. The NHS suggests a non-urgent GP visit for the same reason, and advises seeing a GP before going to a commercial hair clinic.

Minoxidil and Finasteride: How They Work, Side Effects and Who Should Avoid Them

2026-10-15T00:00:00Z

Minoxidil and finasteride are the two medicines most often discussed for pattern hair loss. The NHS describes them as the main treatments for male pattern baldness, with the caveat that they do not work for everyone and only work while you keep using them. They act in very different ways, carry different risks and suit different people. This guide sets out what each one does, where newer options such as low-dose oral minoxidil and dutasteride fit, and who should avoid them.

How minoxidil works

Minoxidil is a prodrug, meaning it has to be converted before it becomes active. A review in Postepy Dermatologii i Alergologii explains that an enzyme in the hair follicle, called sulfotransferase (SULT1A1), turns minoxidil into minoxidil sulfate. Levels of this enzyme vary widely between people, and researchers think this helps explain why some people respond well and others barely respond at all.

Topical minoxidil

Topical minoxidil comes as 2% and 5% products. The same review notes that men typically use 5% once or twice daily, and that in women 2% twice daily has been described as comparable to 5% once daily. The American Academy of Dermatology (AAD) states that both strengths are FDA-approved for women and that results take 6 to 12 months of regular use.

Reported side effects of the topical form include:

Irritant or allergic contact dermatitis on the scalp
Unwanted hair growth elsewhere (hypertrichosis)
A temporary increase in shedding, which the review places around 6 to 8 weeks after starting
Increased hair loss after stopping

The review says topical minoxidil is not recommended during pregnancy or breastfeeding, and the AAD gives the same advice.

Low-dose oral minoxidil

Oral minoxidil was developed as a blood pressure drug. A 2025 narrative review in the Journal of Clinical Medicine states that it is FDA-approved only for severe, treatment-resistant high blood pressure, so using it at low doses for hair loss is off-label. The review summarises the doses reported in the literature.

	Women	Men
Typical starting dose	0.5 mg or 0.625 mg daily	2.5 mg daily
Usual maintenance dose	About 0.5 to 1 mg daily	About 2.5 to 5 mg daily
Maximum reported in the review	2.5 mg daily	5 mg daily

The same review reports these adverse events:

Unwanted hair growth: about 15% in the largest study, dose-dependent and more often noticed by women
Fluid retention or leg swelling: 1.3% to 10% across studies, usually appearing in the first one to three months
Headache: 0.4% to 9%
Fast heart rate: about 0.9% to 4%, usually mild and early
Dizziness: about 1% to 1.7%, usually in the first week

According to the review, most of these resolved after a dose reduction, without stopping treatment. The authors list pheochromocytoma (a rare adrenal tumour) and allergy to the drug as contraindications. They do not recommend low-dose oral minoxidil after a recent heart attack, with heart failure involving reduced pumping function, with severe heart valve disease or with advanced kidney disease without specialist input. They advise caution in people with high blood pressure, irregular heart rhythm, low blood pressure on standing, existing swelling or pericardial disease. Routine blood tests are not required, but the review suggests checking heart history and blood pressure before starting.

How finasteride works

DermNet describes finasteride as a type II 5-alpha reductase inhibitor. It blocks the conversion of testosterone to dihydrotestosterone (DHT), the hormone that drives male pattern hair loss, lowering DHT by up to 70% in the blood and 60% in the scalp. The usual dose for hair loss is one 1 mg tablet a day.

DermNet notes that three months or more of daily use may be needed before any effect shows, and that treatment probably has to continue indefinitely. When it stops, DHT rises again and hair loss is likely to resume.

Side effects

In trials summarised by DermNet, sexual side effects were uncommon and generally resolved after stopping:

Side effect	Finasteride	Placebo
Decreased libido	1.8%	1.3%
Erectile dysfunction	1.3%	0.7%
Reduced ejaculate volume	0.8%	0.4%

Breast enlargement has also been reported. After the drug reached the market, there were reports of depression and, more rarely, anxiety, panic attacks and suicidal thoughts. DermNet also points out that finasteride lowers PSA, a blood test used in prostate cancer screening, by about 50% on average, which matters for anyone having that test.

Oral versus topical finasteride

The FDA has approved only oral finasteride tablets. In an April 2025 alert, the agency stated that no topical finasteride product is FDA-approved and that compounded topical versions have not been evaluated for safety, effectiveness or quality. It received 32 adverse event reports for these products between 2019 and 2024, and many reported effects continued after people stopped using them.

Dutasteride

Dutasteride blocks both type I and type II 5-alpha reductase. The SULT1A1 review reports dose-dependent results at 0.5 mg a day and above, and describes it as more effective than finasteride with comparable side effects. The AAD lists it among tablets sometimes prescribed for female pattern hair loss, while noting that it is not FDA-approved for that use. The review advises women of reproductive age to use contraception during treatment and for six months afterwards.

Who should not use them

Pregnancy: DermNet states that women who are or may be pregnant must not use finasteride because it can cause genital abnormalities in a male fetus. The FDA adds that women should not handle crushed or broken tablets, and that topical products carry a higher risk of transfer to other people through skin contact.
Women in general: The NHS says women should not use finasteride. The AAD notes that some dermatologists prescribe these tablets to women off-label, with birth control for anyone who could become pregnant.
Children: DermNet states that finasteride is not indicated for children.
Heart and kidney conditions: see the cautions for oral minoxidil above.
Breastfeeding: the AAD advises avoiding topical minoxidil during pregnancy and breastfeeding.

Can tretinoin boost topical minoxidil?

Because minoxidil depends on follicle sulfotransferase, researchers have looked for ways to raise that enzyme. The SULT1A1 review describes a small study by Sharma and colleagues in which topical tretinoin changed follicular sulfotransferase expression, and 43% of people predicted to be non-responders to minoxidil became predicted responders after five days of tretinoin. The review treats this as a possible add-on approach and notes that the supporting evidence is still limited. Anyone considering the combination should discuss it with a dermatologist first.

Bottom line

Topical minoxidil is widely available and suits most adults who are not pregnant or breastfeeding. Oral minoxidil, finasteride and dutasteride are prescription decisions that depend on sex, pregnancy plans and heart history. All of them need months of steady use and stop working when they are stopped.

Female Pattern Hair Loss: Signs, Causes, Diagnosis and Treatment

2026-10-05T00:00:00Z

Female pattern hair loss (FPHL) is the most familiar reason women notice thinner hair over time. It rarely looks like the receding hairline and bald crown that many people picture when they think of balding. Instead it tends to show up slowly, along the part, and it is easy to dismiss for months. This guide covers how it presents, what is known about its causes, how a dermatologist confirms it and what the treatment options look like.

How female pattern hair loss presents

The American Academy of Dermatology (AAD) lists a few early signs. The part gets wider, hair near the temples may recede, and a ponytail can feel thinner than it used to. Without treatment some women go on to develop widespread thinning, although women typically do not lose all their hair.

DermNet describes the condition as diffuse thinning of scalp hair, caused by increased shedding, reduced hair volume or both. A review in the International Journal of Endocrinology and Metabolism adds that it most often affects the top of the head and the upper sides, and that the frontal hairline is usually preserved. That preserved hairline is one of the main visual differences from male pattern hair loss.

Recognised patterns

The same review describes three patterns seen in women:

Ludwig type: diffuse thinning over the crown with the front hairline kept intact.
Christmas tree pattern: thinning that widens toward the front of the central part, producing a triangular shape.
Hamilton type: recession at both temples, closer to the male distribution.

The Sinclair stages

Cleveland Clinic outlines a five-stage scale that clinicians use to describe severity:

Stage	What it looks like
1	Little or no hair loss
2	A slight gap at the center part
3	A wider center part, with thinning on either side
4	Bald spots toward the front of the hairline
5	Advanced hair loss

Who gets it and when

The AAD notes that FPHL usually begins in midlife, in the 40s to 60s, though it can start earlier. Cleveland Clinic says it can begin in the 20s or 30s and that risk rises with age, with about one-third of women developing it at some point. Both sources describe it as more common after menopause.

What causes it

Genetics

Heredity plays a strong role. The AAD says the tendency can come from either or both parents, and Cleveland Clinic notes that risk is higher when first-degree relatives have hair loss. DermNet describes the inheritance as polygenic and states that genetic testing for balding risk is not currently recommended because it is unreliable.

Hormones

Hormones are part of the picture, though the details are less clear than in men. Cleveland Clinic explains that dihydrotestosterone (DHT), an androgen, is thought to shrink hair follicles. DermNet points out that most women with FPHL have normal blood androgen levels and that the role of oestrogen is also uncertain. A smaller group of women do have raised androgens, often with acne, irregular periods or excess facial and body hair, which can point to polycystic ovary syndrome (PCOS). FPHL is also known as androgenetic alopecia.

How it is diagnosed

The AAD recommends seeing a dermatologist because several other conditions can look similar and need different treatment. In most cases the diagnosis is clinical. Cleveland Clinic describes a scalp exam, a medical history and measurement of the center part and thinning areas.

Tests a dermatologist may use

Dermoscopy (trichoscopy): a magnified view of the scalp. The 2013 review notes that variation in hair shaft diameter affecting at least 20% of hairs is a feature of FPHL.
Hair pull test: gently pulling a small group of hairs. A positive result across the whole scalp suggests that telogen effluvium, a shedding condition, is also present.
Blood tests: DermNet lists sex hormone levels and thyroid function. The review adds ferritin and vitamin D to rule out factors that worsen shedding, and suggests checking for PCOS in women with irregular periods or signs of excess androgens.
Scalp biopsy: DermNet and Cleveland Clinic both list it as an option when the diagnosis is uncertain.

Conditions that can look similar

The review names chronic telogen effluvium, alopecia areata incognito and frontal fibrosing alopecia among the main conditions to rule out. Chronic telogen effluvium causes increased shedding without the follicle shrinking seen in FPHL and does not progress to baldness. Frontal fibrosing alopecia is a scarring condition that pushes the hairline back and can affect the eyebrows.

Treatment options

DermNet states that there is no cure. Treatment aims to slow or stop progression, and some women regrow hair. The AAD adds that treatment works best when started at the first sign of thinning and that results are lost if treatment stops.

Topical minoxidil

The AAD calls topical minoxidil the most recommended option. It is available without a prescription and is FDA-approved for women in 2% and 5% strengths. Results take 6 to 12 months of daily or twice-daily use, and early shedding can happen when treatment starts. Scalp irritation is a common side effect, and women who are pregnant or breastfeeding should avoid it. DermNet notes that the stronger solution is more likely to cause irritation and unwanted hair growth on the face. The 2013 review reports that a 5% foam used once daily was as effective as the 2% solution used twice daily in one trial.

Prescription tablets

The AAD lists spironolactone, finasteride, flutamide and dutasteride as tablets that may help, while noting that none are FDA-approved for this condition. These drugs can cause birth defects, so they are not appropriate during pregnancy, and dermatologists recommend birth control for premenopausal women who take them. The NHS states plainly that women should not use finasteride, and the 2013 review reports that a controlled study of 1 mg finasteride in postmenopausal women showed no benefit. The same review describes spironolactone as an off-label antiandrogen and concludes that the evidence does not yet support routine antiandrogen use. DermNet adds that low-dose oral minoxidil combined with spironolactone has shown improved hair growth and density.

Procedures and cosmetic options

Option	What the sources say
Hair transplant	May suit some women, depending on whether there is enough healthy donor hair (AAD)
Platelet-rich plasma	Under investigation (DermNet); limited evidence (AAD)
Low-level laser therapy	Benefit unproven, though one device has FDA marketing approval (DermNet)
Camouflage	Coloured sprays, hair-bulking powders and wigs (DermNet)

DermNet advises continuing any treatment for at least six months before judging whether it works, and notes that long-term use is usually needed.

Effects beyond the scalp

DermNet links hair loss with psychological distress, including low self-esteem and depression, and Cleveland Clinic suggests a mental health professional may help when it affects emotional wellbeing. The 2013 review also notes an association between FPHL and metabolic syndrome, and recommends that doctors look at overall health as part of the assessment.