Hair Grows in Cycles, Not Continuously
Hair is the fine strands growing from skin. Each follicle works on its own independent timetable.
Hair consists of fine strands growing from follicles in the skin. Each follicle runs its own cycle of growth, transition and rest, independently of its neighbours — which is why humans shed a hundred or so hairs a day without ever going patchy. If the cycles were synchronised, as they are in some animals, people would moult. Scalp hair grows for years before resting, which is why it reaches such length; eyebrow hair rests after weeks.
- Strands from the skin. *Long hair.*
- A single strand. *A grey hair.*
- Follicle — where it grows. *A follicle.*
- Split hairs — quibble. *Splitting hairs.*
- Old English — *hær*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | hair | Hair. |
| Plural | hairs | Hairs. |
| Adjective | hairy | Hairy. |
| Compound | hairline | A hairline. |
| Old English | hær | Hair. |
- She tied her hair back.Grooming.
- We shed about a hundred a day.Fact.
- Stop splitting hairs.Idiom.
The hair growth cycle
- Anagen — active growth, lasting years on the scalp
- Catagen — a short transition as the follicle shrinks
- Telogen — a resting phase before the hair falls
- Each follicle runs its own cycle independently
- Synchronised cycles would mean moulting, as in many mammals
Old English *hær*, of Germanic origin, related to German *Haar*.
Why do we not moult?
Each follicle runs its own independent cycle, so hairs are shed a few at a time rather than all together.
Why does scalp hair grow so long?
Its growth phase lasts years, while eyebrow and body hair rest after weeks, which limits their length.