Explainer
The hair cycle, explained
Every hair on your scalp grows, pauses and rests on its own schedule. Knowing the three phases makes daily hair fall easier to understand.
Each hair grows from a follicle in the skin. At the base of the follicle sits the hair bulb, which surrounds the dermal papilla. The dermal papilla carries the blood supply that the growing hair depends on.12
Hair does not grow continuously. It moves through a cycle with three named phases.2
Anagen: the growth phase
Anagen is when the hair is actively growing. DermNet gives its length as two to six years on the scalp, and estimates that around 85 to 90% of scalp hairs are in anagen at any one time.34 Scalp hair grows about one centimetre a month.5
Catagen: the transition phase
Catagen is a short transition when growth stops. DermNet describes it as lasting one to two weeks.3
Telogen: the resting phase
Telogen is the resting phase. It lasts around three to four months, and at the end of it the old hair is released as a new hair begins to grow.45
Why this matters
Because hairs are always reaching the end of their resting phase, losing up to about 100 hairs a day is normal.4 When many hairs move into the resting phase at the same time, for example after an illness, more hair falls a few months later.4
Sources
- StatPearls (NCBI Bookshelf). Physiology, Hair. accessed 27 Oct 2026
- StatPearls (NCBI Bookshelf). Histology, Hair and Follicle. accessed 27 Oct 2026
- DermNet. Male pattern hair loss. accessed 27 Oct 2026
- DermNet. Telogen effluvium. accessed 27 Oct 2026
- DermNet. Female pattern hair loss. accessed 27 Oct 2026
Educational content. Not medical advice.