Hair Physiology

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The hair cycle

Hair grows in groups of 1 to 4 hairs called hair follicles. We are born with all the hair follicles we will ever have in the scalp(approximately 100,000). Hair follicles replenish themselves by going through three phases, the Anagen phase, Catagen phase and Telogen phase, known as the hair cycle.

Hair Cycle

This is the reason why hair grows to a particular length and thickness. The duration of the Anagen phase, between 2 to 6 years, determines the length of the hair and the hair bulb determines the hair shaft diameter. The growth rate is approximately 1cm per month.

About the Author

Maurice Collins

DR Maurice Collins

Consultant Surgeon
MB, B.Ch, BAO, DLO, FRCSI, FRCS, FRCSEd.
Registered with the Medical Council of Ireland

Dr Collins is Medical Director and Team Principal of Hair Restoration Blackrock. He was educated at Belvedere College Dublin and did his undergraduate medical studies at University College Dublin. After graduating as a doctor he trained in General Surgery and received his Fellowship (FRCSI) in this specialty from the Royal College of Surgeons in Ireland.

Find out more about DR Maurice Collins and our team of doctors and surgeons.