Light-based hair reduction treatments are only effective when hair is in what growth stage?

Light-based hair reduction treatments are effective primarily during the anagen stage, also known as the active growth phase of hair. During this phase, hair follicles are actively producing hair, which allows the light energy from the treatment to be effectively absorbed by the pigment (melanin) in the hair. This absorption converts the light energy into heat, which then damages the follicle, inhibiting future hair growth.

In contrast, the other stages of hair growth do not provide the same opportunity for effective treatment. The telogen stage is the resting phase, where hair is not actively growing and is more likely to be shed. The catagen stage follows the anagen phase, marking a transitional period where hair growth slows, and the hair follicle shrinks, making it less responsive to light-based treatments. Lastly, the transition phase does not represent a distinct growth stage recognized in hair biology, further emphasizing the specificity of the anagen phase in light-based hair reduction effectiveness. Thus, targeting the anagen stage ensures the best outcomes in hair reduction therapies.