How does LASH DOCTOR actually work? Why does the serum work quicker for some and slower for others? And how does our LASH DOCTOR GROWTH SERUM work with the natural lash cycle?


Most of us have 90 – 160 lashes on the upper lash line, distributed among five to six rows. The lower lash line can have up to 80 eyelashes.

Each eyelash is made up of a hair shaft (the lash you see), a root beneath the skin, and a bulb where the new hair begins growing. The bulb is connected to the dermal papilla (blood supply) which nourishes the lashes so they can grow.

Although we love lashes for their eye-framing drama, they also have a purely functional purpose. Eyelashes are extra sensitive to touch, and when an object or particle touches them, they send automatic signals to the brain to close the eye. Lashes also help filter sunlight and shield the eyes from any unwanted debris or sweat.

Fun fact: eyelashes are the most pigmented of all human hair, which is why they don’t turn grey with age (unlike the hair on our head!)


Eyelashes go through three distinct phases in their growth cycle: Anagen (active growth), Catagen (transition), and Telogen (resting). The complete cycle can take anywhere from four to eleven months to complete.  

Keep reading for how the phases work, our lash serum’s role in each phase, and how your time-to-results can change depending on where you are in the cycle when you start your serum.


In this phase, the hair is attached to the dermal papilla (blood supply) which ‘feeds’ the lash and helps it grow. About 35-40% of the upper lashes (and 15% of lower lashes) will be in the growth phase at one time – this ensures you don’t lose all your lashes at once when the falling-out phase starts.

The Anagen phase lasts for 4 – 10 weeks, where lashes will grow at a rate of 0.12 to 0.14 mm per day. The longer an eyelash stays in the growth phase, the longer it will grow.

THIS IS WHERE LASH DOCTOR comes into play – our serum works to extend the duration of this phase so lashes can continue growing for longer.

Keep in mind, only 40% of your lashes may be in this phase at one time, so when you start a lash serum, you’ll likely see increased length/new lashes on a portion of your lashes, while the other 60% cycle through the other phases.


In this phase, the hair follicle shrinks, detaches from the blood supply, and the eyelash stops growing. Named the ‘transition phase’, lashes maintain length gained from the Anagen phase while waiting for the next phase. This stage lasts for 2 – 3 weeks.

If an eyelash unnaturally falls out (or is pulled out) during this phase, that follicle stays empty while it completes this phase and moves on to Telogen. That means you’ll have an empty spot until that follicle reaches the Anagen phase again.

Our serum’s role in this phase: Length is one thing, but fullness is another. It’s essential to keep lashes strong and healthy so that they don’t fall out during this stage and leave gaping holes in the lash line. Our serum creates supple, non-brittle, nourished lashes that won’t easily break or fall out. This means you have more lashes in place at any one time, creating a fuller lash line.

Lash Biology FAQs


In this phase, lashes sit dormant and rest while a new baby hair begins to grow inside the follicle and the old lash sheds naturally. This stage lasts for 3 to 4 months before the eyelash falls out and re-enters the active growth phase. Approximately 50% of eyelashes will be in this phase at one time. 

Our lash serum works to speed up the Telogen phase so lashes can return to the growth phase sooner.


It all depends where your lashes are in the cycle when you start the serum. While 35 – 40% of your lashes may be in the growth phase (which is being extended by the serum), the other 60% need time to move through the cycle before returning to the growth phase. It also depends on whether your lashes are at the beginning, middle, or end of each phase when you start. 

The best-case scenario for the fastest results: you’ve started the serum when 40% of your lashes are finishing Anagen (growth), and 50% of your lashes are just completing the Telogen (resting) phase. In this case, the serum would extend the growth phase for that 40% and rush the other 50% back into Anagen again. In the reverse situation, if 50% of lashes were just starting Telogen, there would a 4-8 week lag before those lashes returned to the growth phase again. 

This is why many people will notice fullness (more lashes along the lash line) before length. Our lash serum helps prevent breakage or premature fallout in the Catagen and Telogen phases, meaning you’ll have more lashes overall.

It can take about 4-8 weeks to fully replace an eyelash, so if 50% of your lashes are starting Telogen when you begin the serum, it can take that long to see added length in those lashes. In other words, be patient – the payoff is coming!


As we age, the lash cycle slows down and it takes longer for new lashes to regenerate. Also, eyelashes lose their ability to retain moisture as effectively, often resulting in damage to the follicle. Our lash serum is effective in both of these circumstances, however, results are often slower to appear with advanced age. Allow 12 weeks of consistent use to see full, fabulous results!