Telogen effluvium: sudden, diffuse hair loss explained

A different kind of hair loss

Not all hair loss is hereditary. Telogen effluvium is a diffuse hair loss in which an unusually large number of follicles switch to the resting phase (telogen) at the same time and subsequently fall out, evenly across the whole head, not in the hereditary Norwood pattern.

You typically see more hair in the brush, on the pillow and in the drain, and the parting can look wider. Because the loss is spread out, you rarely go completely bald from it, the hair simply becomes thinner all over.

The typical triggers

Telogen effluvium is the body's reaction to a strain. The most frequent triggers are:

• Physical stress, serious illness with fever, surgery, an accident
• Psychological stress, crises, grief, prolonged strain
• Hormonal shifts, childbirth (postpartum), stopping the contraceptive pill
• Severe weight loss and a one-sided diet or deficiencies (low ferritin)
• Thyroid disorders and certain medicines

The 2-3 month delay

An important, and often confusing, detail: the hair loss comes not at the same time as the trigger, but typically 2-3 months later. The follicles first have to pass through the resting phase before the hairs come loose.

That is why many people do not connect the loss to the right cause. If you feel the hair is suddenly falling for no reason, think back to what happened a couple of months ago, the explanation often lies there.

The prognosis is good

The good news is that telogen effluvium is almost always reversible. Once the trigger is removed or has eased, the follicles resume their normal cycle, and the hair typically grows back over 3-6 months. It leaves no scarring and rarely requires treatment beyond removing the cause and ensuring good nutrition (iron, protein).

When you should investigate further

If the loss continues beyond 6 months (chronic telogen effluvium), or you are in doubt whether it is actually early hereditary hair loss, you should act. Have your ferritin, vitamin D and thyroid function (TSH) measured, and let a doctor assess the pattern.

Telogen effluvium and androgenetic alopecia can occur at the same time and reinforce each other. If you want to be sure you know the real cause behind your hair loss, start with the overview of the different types of hair loss.

How to tell it apart from hereditary loss

Because the treatment is so different, it is important to distinguish telogen effluvium from androgenetic alopecia. The clearest differences are:

• Pattern: telogen effluvium is diffuse across the whole head; hereditary loss affects the temples and crown
• Course: telogen effluvium is sudden and often temporary; hereditary loss is gradual and persistent
• Trigger: telogen effluvium usually has an identifiable cause 2-3 months beforehand

The two can occur at the same time and reinforce each other. If you are in doubt, have your ferritin and thyroid function measured, and see the other types in the overview of hair loss.

A practical clue: if you can point to a specific strain 2-3 months before the loss began, and the thinning is even across the whole head, that argues strongly for telogen effluvium rather than hereditary loss, and therefore for a good prognosis.