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How does hair grow?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Hair growth consists of three distinct phases. The growth phase, or anagen, typically lasts from 3-6 years, during which time the keratin hair shaft grows by about one-half inch per month. The transitional phase, or catagen, generally lasts 2-3 weeks, during which hair growth stops and the associated hair follicle shrinks and moves into the next phase. The resting phase, or telogen, lasts for 1-3 months, during which the hair shaft remains connected to the associated hair follicle and no further growth occurs. Afterward, the hair shaft falls from the hair follicle, and in healthy follicles, the cycle moves into another growth phase. Roughly 90 percent of healthy hair follicles are in the growth phase and as many as 10 percent are in the resting phase at any given time.

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Hair goes through its own growth cycle that's unrelated to seasons or hormones or anything else. It's a random biological process that's largely dictated by your genetic disposition. The two main phases of hair growth:
  • Anagen (active): Cells in the root are dividing quickly and pushing the hair out. It averages two to three years.
  • Telogen (resting): This phase lasts for about 100 days on the scalp. Consider it hair hibernation - the follicle is completely at rest.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.