During which phase of eyelash growth should extensions not be applied?

Eyelash extensions should not be applied during the telogen phase, which is the resting phase of the hair growth cycle. During this phase, eyelashes are not actively growing and are more likely to shed naturally. The hair follicles are essentially inactive, making it an unsuitable time for applying extensions, as they would not adhere well and are at a higher risk of falling out along with the natural lashes.

In contrast, during the anagen phase, lashes are actively growing and are best suited for extensions since they provide a stable base for the application. The catagen phase is a transitional phase where growth stops, and the hair follicle shrinks, but there may still be some potential for applying extensions compared to the telogen phase. The exogen phase is associated with the shedding of old hair, but it is not ideal for extensions either due to the instability of the lash.

Overall, applying extensions during the appropriate growth phase ensures the best results and longevity of the extensions.