How much hair loss is normal
Losing up to 100 hairs a day from the scalp is normal: new ones grow in their place. It is a problem when you clearly lose more than usual, notice receding temples or a widening part, or see bald patches. There are many possible causes and they cannot be told apart from a description: an examination is needed, and often tests.
Hair loss in women
In women, hair more often thins evenly, especially around the part, while the front hairline is usually kept. A common cause is inherited thinning (female pattern hair loss). Shedding can also come with hormonal changes, thyroid problems, low iron, a diet with fast weight loss, or tight hairstyles that keep pulling on the hair. If it comes with changes in your cycle, see Irregular periods. For constant tiredness, which may go with low iron or thyroid problems, see Fatigue.
Hair loss in men
In men it is most often inherited baldness: receding temples and thinning at the crown develop gradually over years. It is not harmful to health, but it does not go away on its own. If hair falls out suddenly, in clumps, or you notice smooth round bald patches, the cause may be different and it is worth seeing a doctor.
Hair loss after childbirth, illness and stress
Heavy but temporary shedding often starts 2 to 3 months after a serious illness, a high fever, surgery, childbirth, severe stress or rapid weight loss. Hair falls out all over the head and then slowly regrows once the cause is gone. Even so, with marked shedding it is better to rule out low iron and thyroid problems.
Hair loss in patches and clumps
If round or oval smooth patches without hair appear, it may be alopecia areata, in which the immune system temporarily acts against the hair follicles. It sometimes affects eyebrows and eyelashes. Seeing a dermatologist early helps choose a treatment, and in some people hair regrows by itself. A red, scaly or painful scalp with hair loss is also a reason to see a doctor, to rule out a fungal or inflammatory problem. For an itchy scalp, see Itching; for dry skin, Dry skin.
Hair loss in children and teenagers
Visible hair loss or bald patches in a child are not a normal variation. Causes range from a fungal scalp infection to alopecia areata and the habit of pulling out hair. Take your child to a pediatrician or a dermatologist and do not try to treat it yourself.
What you can do before the visit
- Do not fall for commercial offers of "treatment" before a doctor finds the cause.
- Avoid tight hairstyles, and go easy on hot styling and harsh dyes.
- Eat a varied diet and avoid crash diets: rapid weight loss alone can cause shedding.
- Do not start iron or other supplements on your own: too much can be harmful, and a shortage needs to be confirmed by a test.
- Take photos of the top and sides of your head a month apart, and note when the loss began and what came before it (illness, childbirth, stress, new medicines).
How a doctor finds the cause
The doctor asks when the loss began, about diet, medicines, the menstrual cycle and family history, and examines the scalp and hair, sometimes with a dermatoscope (trichoscopy), and may do a simple hair pull test. Tests usually include a blood count, iron and ferritin, and thyroid-stimulating hormone (TSH), with sex hormones if indicated. Treatment depends on the cause: a shortage is replenished, hormonal problems are treated, and for inherited hair loss there are products applied to the scalp and other methods. They work only for as long as they are used, so choose them together with a doctor.