Thinning hair in teenage girls: causes parents should know

Noticing that a teenage daughter's ponytail feels thinner, or finding more hair than usual in the shower drain, can be worrying for a parent. It can be even more upsetting for the teenager, at an age when appearance and fitting in matter a great deal. The good news is that many causes of thinning hair in teenage girls are common, can be identified with a careful history and examination, and are treatable or settle on their own. This guide explains the main causes, the clues that help tell them apart, what a doctor may check, and how parents can support their daughter along the way.

(This article is general health information. It does not replace an assessment by a doctor who can examine your child.)

Short answer

Thinning hair in teenage girls has several common causes. Reviews of hair loss in children and adolescents list alopecia areata, scalp ringworm (tinea capitis), androgenetic alopecia (pattern thinning), traction alopecia from tight styles, trichotillomania (hair pulling) and hair cycle disturbances such as telogen effluvium as the main ones ¹. In teenage girls, also think about low iron, especially with heavy periods, strict dieting or eating disorders, thyroid problems and polycystic ovary syndrome (PCOS) ^{2 3 4 5}. The pattern matters: patches suggest alopecia areata, ringworm or pulling; all-over shedding suggests telogen effluvium; thinning on top with a widening part suggests pattern thinning. A doctor can usually narrow it down with a history, a scalp examination and, where needed, a few blood tests or a fungal test ¹. See a doctor if hair loss is patchy, the scalp is red or scaly, shedding lasts more than a few months, or there are other symptoms.

Why teenage hair loss deserves attention

Hair loss in children and adolescents often looks different from adult hair loss, and the causes are not always the same ^{1 6}. Teenagers are also going through big changes: puberty hormones, growth spurts, periods starting, exam stress, new diets and new hairstyles. Any of these can play a part.

The emotional side matters too. A systematic review of alopecia areata in children and adolescents found that hair loss was linked with lower self-esteem, emotional distress and social difficulties ⁷. A review of hair loss in young people stresses that psychosocial support is part of good care, because treatment only exists for some conditions and does not always work ¹. Taking a teenager's worries seriously, without adding to her anxiety, is a good first step.

The common causes

Alopecia areata (patchy hair loss)

Alopecia areata is an autoimmune condition in which the immune system targets hair follicles. It usually causes smooth, round bald patches on the scalp, which may appear quickly. It is one of the most common causes of hair loss in young people ¹. Hair often grows back in patches, but the condition can come and go. For more, see Alopecia areata (patchy hair loss): a clear explainer.

Scalp ringworm (tinea capitis)

Tinea capitis is a fungal infection of the scalp. It can cause scaly patches, broken hairs, itching and sometimes tender swelling. It is more common in younger children, but it does affect teenagers. In one Indian hospital study of 170 children with scalp hair loss, tinea capitis was the most common cause among those with non-scarring hair loss, followed by alopecia areata and telogen effluvium ⁶. These figures come from one region and may not match Malaysia, but they show that infection is worth ruling out. A doctor can confirm it with a simple fungal test, and it needs prescription antifungal tablets, not just shampoo ¹. See Scalp ringworm (tinea capitis): signs and treatment.

Telogen effluvium (shedding after a trigger)

Telogen effluvium is temporary, all-over shedding that usually starts about 2 to 4 months after a trigger. Common triggers include a high fever or illness, major stress, rapid weight loss, surgery and some medicines ⁸. Hair comes out at the root, often with a small white bulb, and the overall volume falls, but there are no bald patches. In most cases shedding settles within several months once the trigger has passed ⁸. For teenagers, an illness with a high fever, exam pressure and crash dieting are worth thinking about. See Sudden, severe hair fall: common causes and when to worry.

Pattern thinning (androgenetic alopecia)

Pattern thinning is usually thought of as an adult problem, but it can start in the teenage years. A review of pediatric androgenetic alopecia described it as not uncommon but under-recognised, with a strong link to family history ⁹. A study of 133 young patients in China found signs of it from as early as age 10, and highlighted the importance of checking for hormonal disorders and other conditions alongside the hair ¹⁰. In girls it usually shows as a widening part and thinner hair on top, while the hairline at the front stays in place. See A widening part: early signs of thinning hair in women.

Traction alopecia (tight hairstyles)

Repeatedly pulling the hair tight, for example in high ponytails, tight buns, braids or hair extensions, can damage follicles over time ¹¹. Early signs include thinning or broken hairs along the hairline and at the temples, and small bumps around follicles. Caught early, it often improves once the tension is reduced; long-term tension can cause lasting damage ¹¹. Tight school or sports hairstyles worn every day are worth a look. See Traction alopecia: how tight styles cause hair loss.

Trichotillomania (hair pulling)

Trichotillomania is a condition in which a person repeatedly pulls out their own hair and finds it hard to resist the urge. It typically begins in childhood or adolescence ¹². It may cause irregular patches with hairs of different lengths, often on the side of the dominant hand. Many teenagers feel ashamed and hide it. Behavioural therapy, especially habit reversal training, has the best evidence ¹². A calm, non-judgemental approach helps far more than telling a teenager to simply stop. See Trichotillomania: when hair pulling is hard to stop.

Causes linked to health and nutrition

Low iron and heavy periods

Low iron stores are common in girls and women of reproductive age, and heavy periods are one of the main reasons. Low iron has been studied as a possible contributor to hair shedding, and checking iron stores is a routine part of assessing hair loss in women ². Signs of low iron or anaemia can include tiredness, pale skin, breathlessness on exertion and poor concentration. If your daughter's periods are very heavy, last more than about a week or involve flooding, mention this to the doctor. See Anaemia, iron and hair loss: what the link is.

Strict dieting and eating disorders

Rapid weight loss and very restrictive diets are well-known triggers of shedding ¹³. Eating disorders such as anorexia nervosa and bulimia nervosa can show up in the skin and hair, with hair loss, dry skin and brittle nails linked to deficiencies of nutrients such as zinc, iron and vitamins A and C, and to hormonal changes ³. A review of these signs notes that noticing them can help identify an eating disorder earlier ³. If hair loss comes with weight loss, skipped meals, missed periods, excessive exercise or a strong fear of gaining weight, raise it gently with a doctor. See Hair loss after weight loss or dieting: why it happens.

Thyroid problems

Both an underactive and an overactive thyroid can affect hair growth ⁴. Other clues include tiredness, weight change, feeling unusually cold or hot, a racing heart, and changes in periods. A simple blood test can check thyroid function. See Thyroid problems and hair loss: signs to know.

PCOS

Polycystic ovary syndrome is a common hormonal condition that can cause irregular periods, acne, excess hair on the face or body and thinning hair on the scalp. The 2023 international PCOS guideline recognises skin symptoms as a broad feature of the condition and uses separate diagnostic criteria for adolescents and adults, partly because irregular cycles and ovary changes are normal for a time after periods start ⁵. The guideline also highlights a high rate of psychological symptoms and the need for support with emotional wellbeing ⁵. If thinning hair comes with very irregular periods, acne or extra facial hair, ask about PCOS. See PCOS and hair loss: the hormone link explained.

Clues that help tell the causes apart

More than one cause can be present at once. For example, a bout of shedding after an illness can make early pattern thinning more noticeable.

What a doctor may check

A review of hair loss in children and adolescents describes the main steps ¹:

1. History. When it started, how fast, the pattern, recent illness, stress, diet and weight changes, periods, hairstyles, medicines, and family history of hair loss.
2. Examination. A close look at the scalp and hair, including the hair pull test and, where available, a magnified scalp examination (trichoscopy) ^{1 9}.
3. Fungal test. If ringworm is possible, scrapings or plucked hairs may be sent to the lab ¹.
4. Blood tests. Depending on the history, these may include a full blood count, ferritin (iron stores), thyroid function and, if PCOS is suspected, hormone tests ^{2 5}. See Blood tests for hair loss: what may be checked and why.

Most teenagers start with a family doctor (GP). A referral to a dermatologist may be suggested for unclear or persistent cases, and to a paediatrician, endocrinologist or gynaecologist when a hormone problem is suspected.

Treatment depends on the cause

There is no single treatment for teenage hair loss. The aim is to find and treat the cause:

• Ringworm needs prescription antifungal medicine ¹.
• Telogen effluvium usually settles once the trigger is dealt with, such as recovering from illness or restoring regular, balanced meals ⁸.
• Low iron, thyroid problems or PCOS are treated by a doctor, which may help hair as well ^{2 5}.
• Traction alopecia improves with looser styles if caught early ¹¹.
• Trichotillomania responds best to behavioural therapy such as habit reversal training ¹².
• Alopecia areata may be treated by a doctor, depending on how much hair is affected.
• Pattern thinning in young people is sometimes treated with topical minoxidil under medical supervision. It is not formally approved for this age group, but reviews report that it has been used with success and was generally well tolerated in one large group of young patients, with monitoring ^{9 10}. Hormone-blocking tablets are a decision for a specialist.

Avoid buying strong hair loss medicines or supplements online for a teenager without medical advice. High-dose supplements are not a substitute for finding the cause.

Common misconceptions

• "Teenagers are too young for real hair loss." Pattern thinning and other conditions can start in the teens ⁹.
• "It's just stress, it will pass." Stress can trigger shedding, but patches, scaly skin or persistent thinning need a proper check ¹.
• "A strong anti-dandruff shampoo will fix scalp ringworm." Ringworm of the scalp needs prescription tablets ¹.
• "Hair pulling is a bad habit she can just stop." Trichotillomania is a recognised condition and responds to specific therapy ¹².

How parents can help

• Stay calm and listen. Let your daughter describe what she has noticed and how she feels. Avoid comments about her looks or weight.
• Keep a simple record. Note when the hair loss started, any illness or stress beforehand, and take photos in the same light every few weeks.
• Look at hair habits. Encourage looser styles, fewer tight ponytails, and less heat and chemical treatment. See Heat styling and hair damage: safer habits.
• Support regular meals. Balanced meals with enough protein, iron-rich foods and calories help hair. Watch for signs of extreme dieting.
• Ask about periods. Heavy or very irregular periods are worth discussing with a doctor.
• Mind her wellbeing. If she seems low, anxious or withdrawn, or is avoiding school or friends because of her hair, seek support. Hair loss can affect self-esteem in young people ⁷.

When to see a doctor

See a doctor if you notice any of the following:

• Bald patches, broken hairs, or a red, scaly or painful scalp.
• Shedding that lasts more than about 3 to 6 months.
• Thinning that keeps getting worse.
• Other symptoms such as tiredness, weight loss or gain, missed or very heavy periods, acne or excess facial hair.
• Signs of hair pulling or an eating disorder.
• Hair loss that is affecting her mood, sleep or school life.

For a wider look at hair loss in young people, see Hair loss in teenagers: causes and when to see a doctor and Hair loss in children: common causes for parents.

Life in Malaysia

In Malaysia, a teenager with hair loss can start with a family doctor at a government klinik kesihatan or a private clinic, who can examine the scalp, order basic blood tests and refer to a dermatologist or paediatrician if needed. Be cautious with hair products sold online that make dramatic claims, especially for young people; for cosmetics you can check NPRA guidance on notified products ¹⁴. You can check a doctor's registration with the Malaysian Medical Council ¹⁵. For over-the-counter products, see Hair loss products at the pharmacy: what to ask the pharmacist, and for an overview of options see Hair loss treatment in Malaysia: a plain guide to your options.

Bottom line

Thinning hair in teenage girls has many possible causes, from alopecia areata, scalp ringworm and hair pulling to shedding after illness, tight hairstyles, low iron, dieting, thyroid problems, PCOS and early pattern thinning ^{1 2 5}. The pattern of hair loss and other symptoms give useful clues, and a doctor can usually narrow it down with a history, examination and a few tests. Most causes can be treated or settle with time. Support your daughter calmly, look at diet, periods and hair habits, and see a doctor if hair loss is patchy, persistent or comes with other symptoms.

Frequently asked questions

What are the most common causes of hair loss in teenage girls?

Reviews list alopecia areata, scalp ringworm, pattern thinning, traction from tight styles, hair pulling and shedding after a trigger. Low iron, dieting, thyroid problems and PCOS are also worth checking.

Can teenage girls get pattern hair loss?

Yes. Pattern thinning can start in the teens and is linked to family history. In girls it usually shows as a widening part and thinner hair on top.

Can heavy periods cause hair loss?

Heavy periods are a common cause of low iron stores, and low iron has been studied as a possible contributor to shedding. A doctor can check iron levels with a blood test.

Is hair loss a sign of an eating disorder?

It can be one sign. Eating disorders can cause hair loss, dry skin and brittle nails through nutrient deficiencies and hormonal changes. Look for other signs such as weight loss, skipped meals or missed periods.

Will anti-dandruff shampoo treat scalp ringworm?

No. Scalp ringworm needs prescription antifungal tablets. A doctor can confirm it with a simple fungal test.

What should I do if my daughter pulls out her hair?

Stay calm and avoid blaming her. Trichotillomania is a recognised condition, and behavioural therapy such as habit reversal training has the best evidence.

Can teenagers use minoxidil?

Topical minoxidil is not formally approved for this age group, but doctors sometimes use it for pattern thinning in young people with monitoring. Only use it under medical advice.

When should my daughter see a doctor?

If there are bald patches, a red or scaly scalp, shedding lasting more than about 3 to 6 months, worsening thinning, or other symptoms such as tiredness, weight change or period problems.

Educational content. Not medical advice.