In which stage of hair growth is a club hair formed?

A club hair is formed during the catagen stage of hair growth. This stage represents a transitional phase in the hair growth cycle, wherein the hair follicle begins to shrink and detach from the dermal papilla. During catagen, the hair is no longer receiving nourishment from the blood supply, leading to the formation of the club hair. This is characterized by a rounded, tightly packed tip and signifies that the hair will eventually be shed.

Additionally, the anagen stage is the active growth phase, where hair follicles are producing new hair strands. The telogen stage is the resting phase, where the hair is not growing and is preparing to be shed, but it is not forming club hair yet. The exogen stage is the final part of the telogen phase, during which the hair is actually released from the follicle. Thus, the catagen phase is specifically crucial for the formation of club hairs.