How deep under the scalp do hairs go?

The Depth of Hairs

The end product of all the hard work of the hair follicle is the “hair strand” which we all are familiar with. Humans have about 90,000 - 100,000 of these on the scalp. Individuals with hair loss have less.

All of the machinery to make a hair lies below the scalp surface. Hairs typically extend 4-7 mm below the surface. It varies from patient to patient - and even varies to some degree for the same patient. The longest hairs on the scalp are the so called terminal hairs. The lie deep down in the fat layer.

During the process of balding, hairs not only becomes skinnier and skinnier (miniaturized) but they becomes shorter and shorter. The so callee vellus-like hairs of androgenetic alopecia no longer live deep down in the fat layer. Rather these hairs are found higher up in the dermis. These vellus hairs may only be 2 mm long and 10 mm thick in some cases compared to 6-7 mm long and 80 micrometer thick terminal hairs.