SymptomSkin, hair & nails
Hair Loss: What's Causing It?
Hair loss (alopecia) is losing more hair than usual or seeing thinning or bald patches. Losing 50 to 100 hairs a day is normal. The pattern tells you a lot: gradual thinning at the crown or hairline is usually inherited pattern hair loss, sudden heavy shedding 2 to 3 months after illness, childbirth or stress is telogen effluvium, and round smooth patches suggest alopecia areata. Thyroid disease, iron deficiency and medicines are common, treatable causes.
Also called: Alopecia, baldness, hair thinning, hair shedding
At a glance
- What it is
- Thinning, shedding or patches of missing hair on the scalp or body.
- Most common cause
- Inherited male or female pattern hair loss.
- Other common causes
- Shedding after stress, illness or childbirth, alopecia areata, thyroid disease, iron deficiency, medicines.
- Diagnosis
- Scalp exam, pull test, blood tests, sometimes a scalp biopsy.
- Treatment
- Depends on cause: minoxidil, finasteride, treating deficiencies, steroid injections, or time.
When to get help
See a doctor within a day or two
- Hair loss with a red, swollen, painful scalp with pus or boggy swelling (possible kerion, a severe fungal infection)
- Hair loss with new fever, joint pain, mouth sores or a facial rash (possible lupus)
Book a routine appointment
- Sudden heavy shedding, or patches of complete hair loss
- Thinning with fatigue, weight change, feeling cold or heavy periods
- Hair loss with acne, irregular periods or new facial hair in women
- Scaly, itchy patches with broken hairs, especially in children
- Scarring, shiny scalp, or loss of eyebrows and eyelashes
Usually safe to manage at home
- Normal shedding of up to about 100 hairs a day, more on wash days
- Shedding that started 2 to 3 months after a fever, surgery or childbirth, and is slowing
Is my hair loss normal?
Each hair grows for 2 to 7 years, rests, then falls out and is replaced. About 50 to 100 hairs shed every day, often more after a wash or brushing. Signs that shedding is abnormal:
- a widening part or more visible scalp
- a receding hairline or thinning at the crown
- clumps of hair in your hands, pillow or drain
- smooth bald patches
- broken hairs or scaly patches
Causes of hair loss by pattern
| Pattern | Likely cause |
|---|---|
| Gradual thinning at the temples and crown (men) | Male pattern hair loss |
| Widening part, thinning on top, hairline kept (women) | Female pattern hair loss |
| Diffuse heavy shedding all over, sudden | Telogen effluvium, medicines, thyroid |
| Round, smooth, coin-sized bald patches | Alopecia areata |
| Scaly patches with broken hairs, children | Scalp ringworm |
| Thinning at the hairline and temples from tight styles | Traction alopecia |
| Patchy broken hairs of varying length | Hair pulling (trichotillomania) |
| Shiny scarred patches without follicles | Scarring alopecia |
Pattern hair loss
Androgenetic alopecia affects most men eventually and many women, especially after menopause. Hair follicles shrink under the influence of hormones and genes, producing thinner, shorter hairs. It is gradual and does not cause complete patches.
Telogen effluvium
A shock to the body pushes many hairs into the resting phase at once. About 2 to 3 months later, they shed heavily. Triggers include high fever, COVID-19 and other infections, surgery, childbirth, crash dieting, severe stress and stopping birth control pills. It usually recovers within 6 months, though regrowth takes longer to show.
Alopecia areata
An autoimmune condition where the immune system attacks hair follicles, causing smooth round patches that can appear quickly. Short "exclamation mark" hairs at the edges are typical. Many patches regrow within a year. It can occasionally affect the whole scalp or body. See alopecia for the different forms.
Medical conditions
- Iron deficiency anemia: common in women with heavy periods. Low iron stores (ferritin) are linked to shedding.
- Thyroid disease: both underactive and overactive thyroid cause diffuse thinning.
- Polycystic ovary syndrome: pattern thinning with acne and excess facial or body hair.
- Lupus and other autoimmune diseases.
- Scalp infections: fungal infection (tinea capitis) is common in children.
- Nutritional deficiencies: protein, zinc and vitamin D deficiency. Too much vitamin A also causes shedding.
Medicines and treatments
Chemotherapy causes rapid hair loss that usually regrows. Other culprits include some blood thinners, retinoids, beta-blockers, antidepressants, anti-epileptics, testosterone, and starting or stopping hormonal contraception.
Hair care and habits
Tight braids, ponytails, extensions and weaves cause traction alopecia. Bleaching, relaxers and heat styling make hair break. Compulsive hair pulling causes patchy loss.
How doctors find the cause
A doctor or dermatologist asks when the loss started, any illness, stress or pregnancy in the past 3 months, diet, medicines, periods and family history. They look at the pattern, examine the scalp with a dermatoscope, and do a pull test (gently tugging small bunches to see how many come out).
Blood tests often include a blood count, ferritin, thyroid function, vitamin D, and in women with other hormonal signs, testosterone and related hormones. A scalp biopsy helps with patchy, unclear or scarring hair loss.
Treatment
- Pattern hair loss: topical minoxidil, applied daily, helps men and women maintain and regrow hair. Finasteride tablets work for men. Results take 4 to 6 months, and stopping treatment leads to loss again. Low-dose oral minoxidil and spironolactone (for women) are prescribed by some dermatologists. Hair transplants are an option for stable loss.
- Telogen effluvium: usually no treatment beyond correcting the trigger. Hair recovers on its own.
- Alopecia areata: steroid injections into patches, strong steroid creams, and for severe cases newer tablets called JAK inhibitors.
- Deficiencies and thyroid disease: iron, vitamin D or thyroid treatment.
- Fungal infection: oral antifungal medicine, since creams do not reach the follicles.
- Traction alopecia: loosen hairstyles early, before follicles scar.
Biotin supplements do not help unless you are deficient, which is rare, and they can interfere with thyroid and heart blood tests.
Frequently asked questions
What causes sudden hair loss?
Sudden diffuse shedding is most often telogen effluvium, triggered 2 to 3 months earlier by fever, illness, surgery, childbirth, severe stress or rapid weight loss. Sudden round bald patches suggest alopecia areata. New medicines and thyroid problems are other causes worth checking.
Can stress cause hair loss?
Yes. Severe physical or emotional stress can trigger telogen effluvium, with heavy shedding about 3 months later. Stress can also trigger alopecia areata and hair pulling. Stress-related shedding usually recovers within 6 to 9 months once the stress has passed.
What blood tests check for hair loss?
Common tests are a full blood count, ferritin (iron stores), thyroid function, vitamin D and sometimes zinc. Women with irregular periods, acne or excess hair may have hormone tests. Lupus and syphilis tests are added if symptoms suggest them.
Is hair loss in women different from men?
Women with pattern hair loss usually keep their front hairline and thin across the top with a widening part, while men lose hair at the temples and crown. Women are more likely to have hair loss linked to iron deficiency, thyroid disease, childbirth and polycystic ovary syndrome.
Will my hair grow back?
It depends on the cause. Shedding from stress, illness, childbirth or medicines usually regrows within 6 to 12 months. Alopecia areata often regrows. Pattern hair loss can be slowed or partly reversed with treatment. Scarring alopecia destroys follicles, so regrowth is unlikely.
Sources
This guide was written from current patient and clinical guidance, including:
- American Academy of Dermatology: Hair loss, diagnosis and treatment
- NHS: Hair loss
- MedlinePlus: Hair loss
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Alopecia areata
- British Association of Dermatologists: Telogen effluvium patient information