A developing fetus has all of it's hair follicles formed by week 22. At this time there are 5 million follicles on the body. One million of those are on the head, and 100,000 are on the scalp. This is the largest number of follicles we will ever have - follicles are never added during life. As the size of the body increases as we grow older, the density of the hair follicles on the skin decreases.