Two Mechanisms, Very Different Stakes

Both telogen effluvium and anagen effluvium look the same to a panicking patient: a sudden surge in hair shedding, often visible in the shower drain, on the pillow, or in the brush. The mechanism behind each — and the appropriate response — is completely different.

Telogen Effluvium — The Stress Trigger

In healthy adults, around 10–15% of follicles are in the resting (telogen) phase at any time. A major stressor — illness, surgery, severe diet, childbirth, divorce — pushes a much larger fraction into telogen at once. About 2–4 months later, all those follicles shed together.

Telogen effluvium is almost always reversible. Once the trigger passes, follicles re-enter the growing phase. Recovery takes 6–12 months.

Anagen Effluvium — Direct Toxicity

Anagen effluvium is shedding from follicles still in the growing (anagen) phase. The follicle has been directly damaged — most commonly by chemotherapy, radiation, or severe heavy-metal toxicity. Onset is rapid (within weeks), shedding is dramatic, and the cause is usually obvious.

Recovery depends on the cause. Post-chemo regrowth typically begins 3–6 months after treatment ends and reaches 80% of normal within a year.

Which One Are You Looking At?

Three quick signals separate the two:

• Onset speed: telogen is delayed (months after the trigger); anagen is immediate (weeks)
• Hair characteristics: telogen sheds full-length hairs with white club roots; anagen sheds tapered, broken, dystrophic shafts
• Trigger profile: telogen comes after life stress, illness, or hormonal change; anagen almost always has a chemical or radiation cause

When to Get Bloodwork

For any unexplained shedding lasting more than 8 weeks, get tested: ferritin, full thyroid panel, vitamin D, B12, zinc. Many telogen effluviums are partly nutritional and resolve faster once the underlying deficiency is corrected.