* Growth Phase (Anagen): This is the active growth phase. It lasts for years for scalp hair (typically 2-7 years, which is why hair can grow very long) and shorter periods for other body hair. The length of this phase determines how long the hair can grow.
* Transition Phase (Catagen): This is a short transitional phase (about 2-3 weeks) where the hair follicle shrinks and detaches from the blood supply.
* Resting Phase (Telogen): This is the resting phase (about 3 months) where the hair follicle is inactive and the old hair remains in the follicle.
* Shedding Phase (Exogen): This is often considered part of the telogen phase. The old hair is shed, and a new hair begins to grow from the follicle, restarting the cycle.
So, what does this mean for when hair "stops" growing?
* Individual Hairs: Each individual hair stops growing when it enters the catagen phase. After that, it's just waiting to be shed.
* Overall Hair Growth: Hair growth is a continuous cycle. However, with age:
* The Anagen Phase Shortens: This means hair spends less time actively growing, so it may not reach the same length it did when you were younger.
* Hair Follicles Can Shrink: Over time, some hair follicles can shrink and produce thinner, shorter hairs, or eventually stop producing hair altogether. This is a major factor in age-related hair thinning and balding.
* Hormonal Changes: Hormonal shifts (especially in women after menopause) can affect hair growth patterns and lead to thinning.
In summary:
* Individual hairs stop growing at the end of their anagen phase.
* Overall hair growth slows and may eventually thin due to aging and hormonal changes affecting the hair growth cycle and follicles.
It's important to note that genetics, nutrition, and overall health also play a significant role in hair growth and hair loss.