Telogen effluvium is a type of temporary hair loss caused when a large number of hair follicles shift into their resting phase at the same time, leading to noticeable shedding that typically begins two to three months after a physical or emotional stressor. It is one of the most common causes of diffuse hair loss, and in most acute cases, it resolves on its own within three to six months.
How the Hair Cycle Normally Works
Your hair follicles cycle through three phases independently of each other: a growth phase, a transition phase, and a resting phase. On a healthy scalp, about 85% of hairs are actively growing at any given time, while roughly 15% are in the resting (telogen) phase. Resting hairs eventually fall out to make room for new growth, which is why losing 50 to 100 hairs a day is perfectly normal.
In telogen effluvium, something disrupts this balance. A stressor pushes a disproportionate number of follicles out of the growth phase and into the resting phase all at once. When 25% to 50% of follicles enter the telogen phase simultaneously, the result is dramatic, diffuse shedding, often more than 100 hairs a day. Because resting hairs take two to three months to actually fall out, the shedding doesn’t start until well after the triggering event, which often makes the cause hard to pinpoint.
Common Triggers
The triggers fall into a few broad categories, but they share one thing in common: they represent a significant shock or change to the body.
- Physical stress: Surgery, high fever, serious illness, significant blood loss, or crash dieting can all push follicles into the resting phase.
- Hormonal shifts: Childbirth is one of the most well-known triggers. Post-pregnancy shedding, sometimes called telogen gravidarum, typically begins about three months after delivery. Stopping or starting hormonal birth control can have a similar effect.
- Medications: Certain drug classes, including blood thinners, retinoids, beta-blockers, and some antidepressants, are known to trigger shedding.
- Nutritional deficiencies: Low iron and low vitamin D levels are closely linked to telogen effluvium. One study found that women with this type of hair loss had average iron storage levels (serum ferritin) of about 15 μg/l, compared to 44 μg/l in women without hair loss. Their vitamin D levels were similarly depressed, roughly one-quarter the level seen in healthy controls.
- Emotional stress: The relationship here is less straightforward. Severe psychological stress can contribute, but hair loss itself causes emotional distress, making it difficult to untangle cause from effect.
What the Shedding Looks Like
Telogen effluvium causes diffuse thinning across the entire scalp rather than bald patches or a receding hairline. You’ll notice hair coming out in handfuls in the shower, on your pillow, or gathering in your brush. The frontal hairline typically stays intact, which is one way it differs from pattern hair loss. In some cases, shedding extends beyond the scalp to areas like the eyebrows or body hair, though these areas tend to recover faster.
If you look closely at the shed hairs, they’ll have a small white bulb at the root. This is the telogen club hair, a sign the follicle completed its resting phase normally. The hairs themselves are uniform in thickness, unlike pattern hair loss, where you’d see progressively thinner, finer strands.
How It Differs From Pattern Hair Loss
The distinction matters because the treatments and outlook are very different. Pattern hair loss (androgenetic alopecia) involves follicle miniaturization, a process where hair follicles gradually shrink and produce thinner, shorter hairs over time. In telogen effluvium, the follicles remain healthy and full-sized. The ratio of thick terminal hairs to fine vellus hairs stays close to the normal 7:1. In pattern hair loss, that ratio drops below 4:1.
Pattern hair loss also tends to follow a recognizable distribution: thinning at the crown and temples in men, widening of the part line in women. Telogen effluvium thins the hair evenly across the scalp. It also starts suddenly rather than progressing gradually over years. If your hair loss came on quickly and you can trace it back to a specific event or period of stress two to three months earlier, telogen effluvium is the more likely explanation.
How It’s Diagnosed
Diagnosis is usually clinical, based on your history and a physical exam. One standard tool is the hair pull test: a clinician gently grasps a bundle of about 50 to 60 hairs near the scalp and slides their fingers down the shaft with slow, firm traction. If more than 10% of the hairs in the bundle come out, the test is considered positive, supporting a telogen effluvium diagnosis.
Blood work is often ordered to check for underlying nutritional deficiencies or thyroid problems. Iron storage levels and vitamin D are particularly worth screening for, since correcting a deficiency can speed recovery. A scalp biopsy is rarely needed but can help rule out other conditions if the picture is unclear.
Acute vs. Chronic Cases
Most telogen effluvium is acute, meaning the shedding phase lasts fewer than six months and resolves once the triggering stressor is removed or the body recovers from it. After the shedding stops, new growth begins at the normal rate of about one centimeter per month, so it can take several additional months before your hair feels noticeably fuller again.
Chronic telogen effluvium is defined as shedding that persists beyond six months. It occurs more commonly in women and can be frustrating because a clear trigger is not always identifiable. In chronic cases, the hair tends to fluctuate in fullness over time rather than progressively thinning. Importantly, even in chronic telogen effluvium, follicle miniaturization does not occur, so the condition does not lead to permanent baldness.
Recovery and What Helps
The most effective treatment is identifying and addressing the underlying cause. If a medication triggered the shedding, switching drugs (with your prescriber’s guidance) often resolves it. If a nutritional deficiency is involved, supplementation can help. For post-surgical or post-illness shedding, time is the primary treatment: the body recovers, the follicles re-enter the growth phase, and hair density returns.
Early signs of regrowth include short, fine hairs of normal thickness appearing along the hairline and part. These “baby hairs” are new growth emerging from follicles that have re-entered the active phase. Full recovery of hair density typically takes six to twelve months from the time shedding stops, since hair only grows about half an inch per month.
There’s no way to force resting follicles back into the growth phase faster, so patience is genuinely part of the process. Avoiding aggressive heat styling, tight hairstyles, and harsh chemical treatments can help minimize additional breakage while your hair recovers. Ensuring adequate protein, iron, and vitamin D intake supports healthy regrowth, whether or not a deficiency was the original trigger.