In which stage of hair growth should eyelash extensions not be applied?

Eyelash extensions should not be applied during the telogen stage of hair growth because this is the resting phase in the hair growth cycle. During the telogen phase, the hair is not actively growing, which means it is more prone to falling out. Applying extensions at this stage could lead to increased shedding and an unhealthy appearance of the extensions as the natural lashes are likely to fall out more frequently and unpredictably.

In contrast, applying extensions during the anagen stage, which is the active growth phase, allows for better adhesion as the natural lashes are firmly attached and thriving. The catagen stage, which is a transitional phase, involves the hair follicle detaching from the hair shaft, but it's still more suitable than the telogen phase for extension application. The option "cognition" does not relate to any hair growth stage and is therefore not relevant. Therefore, the best choice for avoiding eyelash extension application is during the telogen phase.