The shortest of the three phases of hair growth is the Catagen phase.

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

Answer: (C)

Understanding the hair growth cycle shows that the catagen phase is the brief transition between active growth and resting. During the growth phase, hair is actively produced for years on the scalp. The catagen phase, however, is short—lasting only a couple of weeks as the follicle shrinks and stops producing hair. After that comes the resting phase, which lasts several months before shedding or new growth begins. Because catagen is such a short transitional window compared with the long growth phase and the longer resting phase, it is the shortest of the three main phases. Exogen is sometimes described as shedding and isn’t counted among the three core phases.