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How does hair grow?

Medicine & HealthLesson on requestFree to readयह पेज हिंदी में पढ़ें

Quick answer

Hair grows from a follicle, a tiny organ in the skin. Cells at the follicle's base divide and push older cells upward; these cells fill with the protein keratin and harden into a strand. Growth occurs in cycles, so each hair grows, rests, and eventually sheds.

Hair grows from a follicle when cells at its base divide and push older cells upward, which harden into a strand. Each follicle cycles through growth, rest and shedding phases, so individual hairs grow at different times.

Step by step

  1. A follicle, a pocket of cells in the skin, produces a hair.
  2. At the follicle's base, matrix cells divide rapidly, adding new cells.
  3. Older cells are pushed upward and fill with keratin, hardening into the hair shaft.
  4. The shaft emerges through the skin surface and continues to lengthen.
  5. After a growth phase, the follicle rests and the hair eventually sheds.
  6. The follicle then re-enters growth and a new hair forms.

Key things to understand

  1. Hair growth starts in a follicle, a tiny pocket of cells sunk into the skin.
  2. At the follicle's base, the hair bulb contains matrix cells that divide rapidly.
  3. These cells push older cells upward, and those cells fill with the protein keratin and harden.
  4. The growing strand extends through the skin surface as a visible hair.
  5. Each follicle cycles through anagen (growth), catagen (transition) and telogen (rest) phases.

Labelled diagram

  1. Anagen

    Active growth phase; matrix cells divide and the hair lengthens.

  2. Catagen

    Transition phase; growth stops and the follicle shrinks.

  3. Telogen

    Resting phase; the hair is held in place but no longer grows.

  4. Exogen

    Shedding phase; the old hair falls out and the cycle restarts.

Hair growth cycle

Real-world examples

  • Scalp hair typically grows about 1 cm per month, so a full head of hair can take years to reach waist length.
  • Eyebrow hairs have a short growth phase, which is why they stay short compared to scalp hair.
  • During chemotherapy, hair often falls out because the drugs target fast-dividing cells, including follicle matrix cells, and it usually regrows after treatment ends.
  • Beard hair starts growing at puberty because androgen hormones switch fine facial hairs to thick, dark ones, and genetics sets how dense it becomes.

Common mistake

✗ Myth: Shaving makes hair grow back thicker and faster.

✓ Fact: Shaving cuts the hair shaft at the skin surface; it does not change the follicle's size, growth rate, or the number of hairs. The blunt tip of a shaved hair can feel coarser, but the hair itself is not thicker.

People also ask

What causes hair to grow?
Hair growth is driven by cell division in the hair follicle. Matrix cells at the base of the follicle divide rapidly, pushing older cells upward. These cells fill with keratin and harden into the hair shaft. Hormones, genetics, and overall health influence the rate and duration of growth.
How long does hair grow in a month?
On average, scalp hair grows about 1 centimetre (0.4 inches) per month. This rate can vary from person to person due to genetics, age, and health. Growth is not continuous; each follicle cycles through growth, rest, and shedding phases, so daily growth may fluctuate.
Why does hair stop growing?
Hair stops growing when its follicle exits the growth phase (anagen) and enters a resting phase (telogen). The hair remains in the follicle for a time and then sheds. After shedding, the follicle re-enters growth and a new hair begins to form, so growth is cyclical.
Why does hair stop growing at a certain length?
Each follicle has a genetically set growth phase that lasts a fixed time. When that phase ends, the hair stops lengthening and eventually sheds, so it never grows beyond the length that its growth phase allows.
Does cutting hair make it grow back thicker?
No. Cutting changes only the visible shaft, not the follicle. The new hair has a blunt tip that may feel coarser, but its thickness and growth rate are unchanged.
Why does hair turn grey?
Hair colour comes from melanin made by pigment cells in the follicle. With age, these cells gradually produce less melanin, so new hairs contain less pigment and appear grey or white.
How fast does hair grow?
Scalp hair grows about 1 centimetre (0.4 inches) per month on average. Growth rate varies with genetics, age and overall health, but this figure is a widely cited typical value.

Part of the guide: How Your Body Works →