Telogen effluvium: sudden, diffuse hair shedding

Telogen effluvium is diffuse, non-scarring hair loss: hair sheds across the entire scalp at once, not in patches and not along a pattern. StatPearls

The name describes the mechanism itself. Telogen is the resting phase of the hair cycle, and effluvium means shedding. What happens: far more strands than usual enter the resting phase at the same time, and shed together months later. The trigger is typically a metabolic strain, a hormonal change, or a medication. StatPearls

The follicles stay intact throughout. The scalp doesn't scar, even during active shedding. StatPearls

"Diffuse" describes the pattern of the shedding: even, across the whole scalp, not in patches and not along a pattern. Telogen effluvium is a non-scarring form of hair loss, characterized by exactly this diffuse, often sudden shedding StatPearls. In practice the two names often refer to the same thing: what a doctor calls telogen effluvium, everyday language refers to as diffuse hair loss.

Not every diffuse picture is telogen effluvium. In women, the pattern (androgenetic) form can also look scattered: the part widens while the frontal hairline stays intact StatPearls AGA. The two can also be present at once, and the wash test below separates exactly this Asghar 2020. Telling it apart from the other forms (patchy hair loss, anagen effluvium, scarring alopecia) is a job for a doctor StatPearls.

If it's shedding suddenly and evenly, you're in the right place, read on. If it's thinning along a pattern: male pattern, female pattern, or the pattern selector.

Every hair strand runs on its own cycle, out of sync with its neighbors. That's why hair doesn't disappear overnight: at any given moment, most strands are growing and a smaller share are resting.

On a healthy scalp, roughly 85 percent of strands are in the growth (anagen) phase, and 15 percent are in the resting (telogen) phase. StatPearls The follicle produces the same strand for almost four years, then rests for about four months while a new strand grows in underneath and pushes the old one out. StatPearls

One review gives slightly different figures: the anagen phase lasts 2-5 years and covers roughly 90 percent of strands, the catagen transition lasts 3-6 weeks, and telogen lasts 3-5 months and covers roughly 10 percent of strands. Asghar 2020 The exact ratio depends on the person and the measurement, but the order of magnitude is the same.

In telogen effluvium, this ratio tips out of balance. On a histology sample, the diagnosis is confirmed when at least 25 but no more than 50 percent of follicles are in the telogen phase. StatPearls

The strand that sheds is itself normal. It falls out at the end of a properly completed cycle, just far more of them at once than usual.

This is the most common misunderstanding around telogen effluvium. The event that triggered it didn't happen when the shedding started.

The trigger sends strands from the growth phase into the resting phase. During the resting phase you see nothing: the strand stays in place, it doesn't grow, but it doesn't fall out either. When the follicle restarts, the new strand pushes the old one out from underneath, and that's when the visible shedding begins. This delay creates the characteristic timing: the triggering event typically happened about 3 months before the shedding started, with a range of 1 to 6 months. StatPearls One review puts it at 2-3 months. Asghar 2020

That's often why by that point you've long recovered from the illness or the surgery is behind you, and it never occurs to you that the two are connected. StatPearls

If your hair is shedding right now, it's worth thinking back over the past six months.

The most common triggers: acute febrile illness, severe infection, major surgery, severe trauma, postpartum hormonal change (mainly the drop in estrogen), hypothyroidism, sudden discontinuation of an estrogen-containing product, drastic dieting, low protein intake, heavy metal exposure, and iron deficiency. StatPearls

The most common medications: beta-blockers, retinoids (including excessive vitamin A intake), anticoagulants, propylthiouracil, carbamazepine, and vaccines. StatPearls One review also lists birth control pills, ACE inhibitors, anticonvulsants, and antidepressants, and states that drug-induced shedding typically starts after 12 weeks of use. Asghar 2020

Both directions matter for the thyroid. Both an underactive and an overactive thyroid can cause telogen effluvium, and the shedding resolves once thyroid function is restored. Asghar 2020

Stress is the most commonly cited cause, and it's exactly the hardest one to work with. The effect of severe physical stress is well documented: surgical trauma, high fever, chronic systemic illness, hemorrhage. Asghar 2020 The link between emotional stress and hair loss, however, is unclear in the literature, partly because hair loss itself is a source of stress, making it hard to tell which one causes the other. Asghar 2020

In roughly a third of acute cases, the trigger is never identified. Asghar 2020

The two look different, have a different mechanism, and a different solution.

In telogen effluvium, the main event is the shedding. It's even, across the whole scalp, and strand thickness stays normal: histologically, neither follicular miniaturization nor perifollicular inflammatory infiltrate is typical. Asghar 2020

In pattern (androgenetic) hair loss, miniaturization is the striking feature. Activation of the androgen receptor shortens the growth phase, so with each cycle the follicles produce a thinner, shorter strand. StatPearls AGA That's why it thins along a pattern: in men at the crown and temples, in women the frontal hairline typically stays intact while the crown thins, which makes the part look wider. StatPearls AGA

There's a simple test to tell them apart. The modified wash test counts the shed strands after five days without washing, and checks what percentage of them are thin, fluff-like (vellus) strands. Asghar 2020 The result falls into one of four categories:

• more than 100 strands, less than 10 percent vellus: telogen effluvium
• less than 100 strands, more than 10 percent vellus: androgenetic hair loss
• more than 100 strands and more than 10 percent vellus: both together
• less than 100 strands, less than 10 percent vellus: normal, or telogen effluvium already resolving

The third row is the important one: the two aren't mutually exclusive. Asghar 2020

There's also a rougher measurement you can do at home. If you collect 100 or more strands over 24 hours without washing your hair, that points to telogen effluvium, and it's worth repeating three to four times a week, since a single day fluctuates a lot. StatPearls During active shedding, a gentle pull test brings out at least four strands in your hand. StatPearls

If the pattern is what interests you, I've written a separate page about it: male pattern hair loss, female hair loss, or the pattern selector, if you don't yet know which one is yours. On the hormonal background: what DHT is, and what it does to the follicle.

In telogen effluvium, the first step is aimed at what triggered it.

If hypothyroidism, a chronic metabolic condition, or iron deficiency is suspected, targeted testing for these is recommended. StatPearls For the thyroid, the signs that warrant a TSH test: fatigue, constipation, weight gain, cold sensitivity. StatPearls

Iron deficiency is measured with a complete blood count, serum iron, iron saturation, and ferritin together. StatPearls Low ferritin confirms iron deficiency, but normal ferritin doesn't rule it out, since ferritin also rises with inflammation. Iron saturation is the most sensitive indicator. StatPearls

The body prioritizes blood production over hair, so hair starts shedding before red blood cell size changes. StatPearls So hair can shed even while blood counts are still normal.

Ordering and interpreting labs is a medical task. It starts with your GP or a dermatologist.

By definition, acute telogen effluvium is shedding that lasts less than 6 months, and it's often far shorter than that. StatPearls Roughly 95 percent of acute cases go into remission. Asghar 2020

If the trigger has been found and treated, no further treatment is needed on its own. StatPearls With a hormonal or nutritional deficiency (iron, zinc, vitamin D) or a metabolic condition, hair growth restarts once these are corrected, and for drug-induced shedding, once the medication is stopped. StatPearls

You need realistic expectations for the timing. Hair growth can take up to 6 months to restart, and even longer before it becomes visible. StatPearls

Shedding that lasts beyond 6 months is chronic telogen effluvium. Asghar 2020 It typically affects middle-aged women, with a prolonged, fluctuating course. Asghar 2020 The cosmetic outcome tends to be good here too, even if the shedding continues. StatPearls

Your hair otherwise stays normal. You can wash and comb it the way you normally would. StatPearls

Postpartum hair loss is the best-known form of telogen effluvium. The literature calls it telogen gravidarum, and it typically appears between the second and fifth month after birth. Asghar 2020 The trigger is the postpartum hormonal change, mainly the drop in estrogen. StatPearls

The measured data, though, is thinner than you'd expect. A 2016 review looked at what had been measured on this so far and found only two studies. In the larger one, 116 women were studied: at four months postpartum, the proportion of strands in the growth phase was 78.5 percent, versus around 81 percent at other time points. A statistically significant but small difference. The review's authors concluded that the true incidence of postpartum telogen effluvium is unknown. Mirallas 2016

This doesn't mean what you're experiencing isn't real. It means nobody has properly measured its extent so far.

Microneedling acts on the environment around the follicle: it opens microchannels in the upper layer of the scalp and triggers a local regenerative response. What's been studied on hair with it was androgenetic hair loss. Dhurat 2013 I haven't found a study done in telogen effluvium that measures hair as the endpoint.

This has a biological reason. In telogen effluvium, the follicles are intact, there's no miniaturization, and strand thickness is normal. Asghar 2020 What's tipped out of balance is the rhythm of the hair cycle. A trigger set it off, and typically resolving that trigger is what restores it. Puncturing the scalp doesn't help with this, and it doesn't speed up the recovery either.

If your hair is suddenly and diffusely shedding right now, the first step is bloodwork and finding the cause.

There's one situation where it does come into play: if both are present at once. The third category of the wash test is exactly this, more than 100 strands and more than 10 percent vellus. Asghar 2020 In that case, the patterned portion is what a treatment against androgenetic hair loss can work on, while the acute shedding runs its own course. The order is still the same: labs and diagnosis first, the device after.

StatPearls states that for telogen effluvium, minoxidil hasn't been proven to restore hair growth, though it has a theoretical benefit, and anyone who wants to actively do something can choose to use it. StatPearls The same source also notes that acute telogen effluvium is a self-limiting condition, so prescribing hair-growth medication or a hair transplant isn't necessary. StatPearls

I have androgenetic hair loss, I'm treating that, and that's why I stamp my scalp weekly. I wrote about the practice here: the 1 mm stamp at home, and on the medication side here: minoxidil, and finasteride and dutasteride.