Hair grows from follicles in the skin, and each strand follows its own cycle.

The longer version

Each follicle operates on its own schedule, which is why neighbouring hairs on the same head can be at completely different stages. A strand grows actively for a period, then the follicle shrinks and the strand stops lengthening, and eventually it is shed and a new one begins underneath.

The visible hair is mostly dead, hardened protein pushed up from the living base; the living part is the root below the skin. Hormones, blood supply and genetics all influence how long the growing phase lasts. Because the cycles are staggered, shedding happens gradually rather than all at once across the scalp.

Where this entry sits

These facts look at how the human body works in ordinary moments, from breathing and blinking to balance and sleep. They focus on anatomy, senses, and small reactions that happen constantly without any conscious effort. The full list sits on the Human Body page, where every entry is listed in order.