We love a two-in-one product, because let's be real, we're all about doing less and getting more.

Multi-function beauty products are everywhere — sunscreens that are also primers and moisturizers, nail polishes that act as strengtheners, leave-in conditioners that have heat-protectant, and the list goes on. However, considering that everyone is obsessed with eyelashes these days, a new type of product is on the rise.

Lash growth eyeliners have started to pop up left and right. Unlike the lash growth serums you apply at night before going to bed, these ones have a strong color payoff and rival your favorite longwear liner.

The idea sounds almost too good to be true, or too obvious to be innovative. So, we tapped two experts to explain what lash-boosting eyeliners are, how they work to make lashes grow, potential side effects, and where to shop for your next go-to eyeliner.

What Are Eyelash-Growth Eyeliners?

As mentioned above, they're liquid eyeliners with lash-boosting ingredients. For anyone looking to streamline their beauty routines, this hybrid product offers the best of both worlds.

"When applying liquid liner, we're already trying to get it as close to the lash line as possible, so lash-boosting liner does two jobs at once," says Los-Angeles-based makeup artist Amber Dreadon.

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How Do Lash Growth Eyeliners Actually Work?

Instead of purely cosmetic ingredients, these new-school eyeliners have follicle-strengthening formulas, such as peptides, which act as building blocks for eyelash growth. And unlike other products on the market, which can make new hairs grow where they didn't exist before, these follicle-strengthening formulas work to extend the life of each lash.

Alison D. Early, MD, a board-certified ophthalmologist and twenty/twenty beauty Visionary Panel member, explains that eyelashes are in a continual cycle of growth and replacement, with a typical lash life cycle about six to 10 weeks. She adds that people tend to shed about five lashes a day. With that in mind, if you're able to extend your lash life by even two weeks, they'll continue to grow and, therefore, reach higher lengths.

Are There Side-Effects Of Using Eyelash-Growth Eyeliners?

Latisse is the only FDA-approved lash-growth serum, as it's the only product that actually makes lashes grow rather than boost growth. While Latisse does require a prescription, Dr. Early points out that there are other non-prescription lash serums containing lower-potency prostaglandin analogues (PGAs), as well as other lash-enhancing compounds.

Since non-prescription aren't regulated in the same way by the FDA, it's always important to look at a product's ingredient list and be aware of potential side effects. "Any cosmetic item could cause a localized contact reaction," says Dr. Early. "Eyelid skin is particularly thin and delicate and may be especially sensitive to irritation." If you experience any redness or irritation after using a product, she urges you to seek an evaluation with your eye doctor.

Where Can You Buy Eyelash-Growth Eyeliners?

Thankfully, there are a few choices to choose from. Check out some of our favorites below:

Freck RocketLash Liner

This is Dreadon's eyeliner of choice, and for good reason. Dr. Early explains that it's a non-PGA product that contains several peptides including B vitamins to aid in lash growth and strength. "I love the vinyl effect of Freck's Liner and the convenience of applying a lash serum and eyeliner in one step," adds the makeup artist.

Grande Cosmetics GrandeLINER

You've all heard of the cult-classic Grande Cosmetics lash-growth serum, and this eyeliner is an extension of that hero product. Dr. Early explains that this formula contains isopropyl cloprostenate, which is a synthetic prostaglandin analogue also used in many eyelash growth serums.

Physicians Formula Eye Booster Lash 2-in-1 Boosting Eyeliner + Serum

This eyeliner is perfect for the summer as it's water-resistant and smudge-resistant, making it ideal for enduring hot and humid temperatures. "[It] contains myristoyl pentapeptide, which can hydrate lashes to make them appear thicker, fuller, and shinier," says Dr. Early of this drugstore pick.

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