Also known as “peach fuzz”, vellus hairs are fine and wispy. Unlike their matured counterparts, which are thick, long, and dark, vellus hairs are thin, short, and contain nearly no pigmentation whatsoever. Vellus hairs also contain no sebaceous glands, which are responsible for secreting moisturizing oils into the hair follicle so that the hair may easily slide upwards through the follicle as it grows.
This type of hair is created in the anagen stage of hair growth. In fact, all terminal hairs are at one point finer and shorter as they come out of telogen and begin the anagen stage where they thicken, enlarge, darken, and otherwise mature. This change occurs in both males and females. However, since males have much more testosterone in their bodies than females, they tend to grow a denser amount of mature hairs throughout the body, particularly around the face, under the arms, and sometimes on the chest as well. It is important to remember that not all vellus hairs become terminal. Both types of hairs can be found on the body at all times. While ethnicity can play a role in the amount of vellus hairs vs. terminal hairs on the body it is generally accepted that males have less vellus hairs on their bodies than compared to females.
Yes, but this is expected for most hairs on the body when they revert back to the telogen phase of growth. Hairs lie dormant for three to five months and then upon regrowth they can appear as fine vellus hairs that are weak and immature. This is usually temporary unless the hairs are being aggressively affected by dihydrotestosterone and the process of male pattern hair loss and miniaturization.
Terminal hairs show no signs of miniaturization. Miniaturization is where dihydrotestosterone (DHT) prevents the hair from receiving nutrition by binding to receptors within the tissue. Once the hair no longer receives nutrition, the hair follicle literally begins to shrink. At this time, the hairs will no longer be as full, thick, or long as they once were. If miniaturization is allowed to continue, the follicle will shrink completely to the point where no hair can grow at all.
Terminal hairs can be stimulated by certain forms of medication. Minoxidil, for example, can cause terminal hairs to grow, although the exact working mechanisms remain unknown. 5aR inhibitors work by preventing the body from making DHT. With less DHT in the body, the hair follicles continue to receive nutrients and grow new hairs as normal. Always consult your doctor before taking a 5aR inhibitor or minoxidil.