Telogen Effluvium – Harvard Health

by Curavital | Dec 10, 2025 | Healthcare, Parkinsonism

What is telogen effluvium?

At any given time, about 85% to 90% of the hairs on the average person’s head are actively growing (the anagen phase) and the rest are resting (the telogen phase). Typically, a hair is in the anagen phase for two to four years, then enters the telogen phase, rests for about two to four months, and then falls out and is replaced by a new, growing hair. The average person naturally loses about 100 hairs a day.

In a person with telogen effluvium, some body change or shock pushes more hairs into the telogen phase. Typically in this condition, about 30% of hairs stop growing and enter the resting phase before falling out. So if you have telogen effluvium, you may lose an average of 300 hairs a day instead of 100.

Telogen effluvium can be triggered by a number of different events, including:

surgery
major physical trauma
greater psychological stress
high fever, severe infection or other illness
extreme weight loss
extreme change in diet
sudden hormonal changes, including those associated with childbirth and menopause
iron deficiency
hypothyroidism or hyperthyroidism
some medications.

Because hairs entering the telogen phase rest in place for two to four months before falling out, you may not notice any hair loss until two to four months after the event that caused the problem. Telogen effluvium rarely lasts longer than six months, although some cases last longer.

Although losing a large amount of hair in a short period of time can be scary, the condition is usually temporary. Every hair that is prematurely pushed into the telogen phase is replaced by a new, growing hair, so there is no danger of complete baldness. Because scalp hair grows slowly, your hair may feel or look thinner than usual for a period of time, but the fullness will return as the new hairs grow in.

Symptoms of telogen effluvium

If you have telogen effluvium, you’ll notice more hair than usual collecting on your pillowcases, on the shower or bathroom floor, and in your hairbrush. Your scalp may feel or look less dense than usual. Often, however, the hair loss is subtle and other people may not notice anything different about your hair.

Diagnosing telogen effluvium

Most cases of telogen effluvium can be diagnosed based on medical history and an examination of the scalp and hair. If the hair loss has been occurring for several months, there may be visible patches of thinning, but often the hair loss is not dramatic enough for a doctor to notice. If you have large bald spots, you probably don’t have telogen effluvium. If the doctor gently pulls on some hairs on your scalp and four or more hairs come out, you probably have telogen effluvium. The hair will also look like hair in the telogen phase – it will have a white bulb at the end that was at the scalp and will not have a gel-like coating around that end of the hair.

You may be asked to collect all the hairs that fall out of your head over a 24-hour period and count them to see if the hair loss is really excessive. Losing fewer than 100 hairs in a day is considered normal. You may also be asked to collect and count lost hairs every or every other week to see when the hair loss starts to slow down.

In some rare cases, if there is reason to doubt the diagnosis, a scalp biopsy may be performed. In this procedure, a small piece of scalp that includes several hair follicles is removed and examined under a microscope. Your doctor may also do blood tests to check for conditions such as thyroid abnormalities that may contribute to hair loss.

Expected duration of telogen effluvium

Typically, hair loss begins two to four months after the event that triggered the problem and lasts about six months. New hair begins to grow immediately after the hair falls out, but significant growth may not be noticed for several months.

Prevention of telogen effluvium

Nothing can be done to prevent most of the types of physical shocks that can start telogen effluvium. Some cases can be caused by a poor diet and these can be prevented by eating a balanced diet that provides sufficient protein, iron and other nutrients.

Treatment of telogen effluvium

No treatment for active telogen effluvium has been shown to be effective.

Some causes of the disorder can be corrected. For example, if you have a poor diet, contact a dietitian to help you balance it. If the hair loss started after you started a new medication, talk to your doctor to see if the medication should be stopped. Many times, however, the cause is a specific event in the past, and you can expect the hair to grow back. In cases where hair growth has not returned to a satisfactory level, your doctor may prescribe minoxidil (Rogaine), a lotion applied to the scalp that can stimulate hair growth in some people.

When to call a professional

See your doctor if you experience excessive hair loss or obvious thin patches on your scalp.

Prognosis

The outlook for telogen effluvium is very good. Most cases run their course within six to nine months, and the hair usually grows back. In some cases, the disorder may last longer. In other cases, not all hair grows back.