This is the phase when lashes are actively growing, and it lasts between 30 and 45 days. Only about 40 percent of the upper lashes and 15 percent of the lower lashes are in the anagen phase at any one time. Each lash will grow to a specific length and then stop.
During this phase, the lash stops growing, and the hair follicle shrinks. If an eyelash falls out or is plucked out during this phase, it won’t grow back right away because the follicle needs to complete the catagen phase before it can move on to the next one. This phase lasts between 15 and 20 days.
This phase can last more than 100 days before the eyelash falls out and a new one begins to grow. Because each individual lash is in its own phase of the growth cycle, it’s normal for a few lashes to fall out most days. It typically takes between four and eight weeks to fully replace an eyelash.