What are the three phases of hair growth?

• A. Anagen, Catagen, Telogen
• B. Growth, Rest, Shedding
• C. Phase I, II, III
• D. Active, Dormant, Replacement

Answer: (A)

Hair grows in a cycle with three phases: anagen, catagen, and telogen. Anagen is the active growth phase where the hair follicle is actively producing hair, and the hair is attached to the follicle with pigment present. Catagen is a short transitional phase in which growth stops and the follicle shrinks, detaching the hair from its blood supply. Telogen is the resting phase where growth pauses and the hair remains in the follicle until it sheds and a new cycle begins. In laser hair removal, treatments are most effective during the anagen phase because the hair contains pigment (melanin) and is actively growing, making it more susceptible to the laser’s energy. Hairs in catagen or telogen are less responsive, which is why multiple sessions are needed to target hairs as they cycle back into anagen.