At any one time, about 90% of scalp hair is in this phase.

• A. Exogen phase
• B. Telogen phase
• C. Anagen phase
• D. Catagen phase

Answer: (C)

Most scalp hair is in the growth phase because this phase lasts much longer than the others. During anagen, the hair follicle is actively producing the hair shaft, with cells in the hair bulb dividing and pushing new hair upward. Because this growth phase can persist for years, about 90% of scalp hairs are in anagen at any given time. This long, ongoing production explains why hair grows long and why most hairs aren’t shed at once.

In contrast, the next phase is a brief transition (catagen) where growth stops and the follicle shrinks, and then a resting phase (telogen) where hairs are not growing and may shed later. Exogen is sometimes described as the shedding portion, but it involves a smaller portion of hairs at any moment. So the phase that best fits the statement is the growth (anagen) phase.