Chronic telogen effluvium: when shedding lasts for months

Most episodes of heavy shedding settle on their own once the trigger has passed. But some people, most often women, find their hair keeps shedding for many months with no clear end. This is often called chronic telogen effluvium. Understanding what is known, and what is still debated, can help you get the right checks.

A quick refresher on telogen effluvium

At any one time, about 85% of scalp hairs are in the growing (anagen) phase and about 15% are resting (telogen) ¹. A follicle typically grows hair for almost 4 years and then rests for about 4 months, before a new hair pushes the old one out ¹.

Telogen effluvium happens when a stress on the body pushes many growing hairs into the resting phase at once, so more hairs fall out a few months later ¹. Common triggers include ¹:

• a high fever or severe infection
• major surgery or trauma
• hormonal changes after childbirth, or stopping estrogen-containing medicines
• an underactive thyroid
• crash dieting, low protein intake or iron deficiency
• certain medicines, including beta-blockers and retinoids

The NHS notes that losing between 50 and 100 hairs a day is normal, and that hair loss caused by a medical condition or stress usually stops or grows back once you recover ².

When shedding does not stop

When shedding continues for many months and no clear cause can be found, doctors sometimes use the label chronic telogen effluvium ³. But experts are not sure it is a separate condition at all.

A 2023 systematic review looked at 18 published studies covering 1,628 cases ³. It found:

• 97.5% of cases were women ³.
• No study showed that all possible causes of telogen shedding had been excluded ³.
• Only 3 studies, covering 8 cases, followed people forward over time ³.
• Studies that took scalp biopsies all found a normal ratio of thick to fine hairs in the samples ³.
• There is no agreed, consistent definition of chronic telogen effluvium ³.

What might really be going on

The reviewers suggested several explanations ³:

• Early female pattern hair loss. Pattern thinning can begin with increased shedding before a wider part or thinner crown becomes obvious. See the Ludwig scale and fine hair or thinning hair?.
• A cause that has not been found yet. Low iron, thyroid problems, a medicine or another trigger may still be at work.
• A change in the hair cycle where triggers have truly been ruled out.
• Worry about normal shedding. Some cases may reflect concern about normal shedding in anxious people with long hair, where each fallen hair looks like a lot ³.

None of these explanations means your concern is not real. It does mean a careful search for causes matters more than the label.

Getting the right checks

A doctor will usually want to:

• Take a detailed history. Illness, surgery, childbirth, diet changes, stress and all medicines or supplements in the months before shedding began ¹.
• Examine the scalp. Looking at the parting width, crown and hair calibre helps separate shedding from pattern thinning.
• Arrange blood tests if needed. Common checks look at iron stores and thyroid function. See blood tests for hair loss.
• Review your diet. Crash dieting and low protein intake are recognised triggers ¹.

If a cause is found and treated, shedding often settles over the following months, because hair takes time to cycle back to normal.

Tracking your hair

Because shedding feels alarming day to day, a more objective record helps:

• Take photos of your parting and crown every month in the same light. See tracking hair with photos.
• Note big life events, illnesses and medicine changes with dates.
• Watch for patterns. A widening parting or see-through crown suggests pattern hair loss rather than shedding alone.

Caring for your hair meanwhile

• Use gentle washing and styling, and avoid tight hairstyles and harsh chemical treatments.
• Eat a balanced diet with enough protein, and avoid crash diets.
• Look after sleep and stress where you can. Stress does not explain everything, but it is a common contributor.

When to see a doctor

See a doctor if shedding has lasted more than a few months, if you notice a widening parting or bald patches, or if you have other symptoms such as tiredness, weight change or irregular periods. The NHS advises seeing a GP if you are worried about your hair loss ². A dermatologist can help if the cause is still unclear. For a first overview, see first steps after noticing hair loss.

Frequently asked questions

What is chronic telogen effluvium?

It is a label for long-lasting shedding without a clear cause, but there is no agreed definition and experts debate whether it is a separate condition ³.

Could long-term shedding be pattern hair loss?

Yes. A systematic review suggested many cases may be early female pattern hair loss or a cause not yet found ³.

How many hairs a day is normal to lose?

The NHS says losing between 50 and 100 hairs a day is normal ².

What commonly triggers telogen effluvium?

Fever, surgery, childbirth, thyroid problems, crash dieting, iron deficiency and some medicines are common triggers ¹.

Educational content. Not medical advice.