Latisse - LEAD
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When it comes to the trend in lash length, long is the one to have. But since we’re not all born with Twiggy’s features, getting there often requires some trusty reinforcements. Lengthening mascaras help you fake it, but growth serums help you make it a reality. There are plenty of OTC tubes that promise a boost in length, but there’s likely one prescription all your friends are talking about, and it goes by the name of Latisse.

You probably already know the basics. It's a prescription-only lash growth serum that works to increase your length, and according to the brand, can make your lashes fuller and darker. But we wanted specifics, so we went to a dermatologist for answers on how it really works.

"It works on the active ingredient bimatoprost at a concentration of 0.03%," says dermatologist Dr. Kavita Mariwalla. "This is a prostaglandin analog which is used for hypotrichosis of the eyelids—not enough lash hair. This is the same ingredient used to treat narrow angle glaucoma, which is how it was discovered. Men with glaucoma would come in and have these beautifully long eyelashes all of a sudden."

In Dr. Mariwalla's opinion, it can increase the length of your lashes but not necessarily the density, or how many you have, and she feels like it can be effective in enhancing the thickness of your brows, though it's not marketed to that area of the face.

The process of applying it seems relatively simple. The product comes in a dropper and is applied via a disposable applicator on the area of your eyelid where the skin meets the lashes. But don't expect to wake up with doe-eyed lashes à la Mariah Carey. It's a gradual process that requires consistent use, and the brand claims it takes about 16 weeks to see the full effects.

And if you already have long lashes but want to amp it up, Dr. Mariwalla says she's seen success there, too.

"There does seem to be some stop mechanism, however, so with continued use it's not like your lashes will touch your forehead, says Dr. Mariwalla. And as you stop using it, your lashes will slowly return to their natural length.

VIDEO: 4 Ways to Apply At-Home Eyelash Extensions

Like any treatment, there are some possible concerns and potential side effects like eyelid puffiness, itching, irritation, and Dr. Mariwalla explains there's a chance of eye discoloration, though she hasn't seen this happen. "What I have seen is a hyperpigmentation of the area where the Latisse is placed, which almost makes it look like you are wearing eyeliner on the top lid when you are not. Again this is a fraction of patients, but something I warn everyone about."

So if you can stick to a schedule and want longer lashes without booking an extension refill every three weeks, talk to your doc about getting Latisse.