K, here’s the thing: Even though OTC eyelash serums (which are usually formulated with moisturizing ingredients like vitamin E or castor oil) can help hydrate and strengthen your lashes, they can’t technically make them grow. That said, if you’re trying to grow your eyelashes longer, you can still help the natural process along by investing in a good serum that’ll help cut down on breakage and shedding. “Lash conditioners may help strengthen lashes, prevent them from breaking, or lightly swell them so they look a little thicker,” says Ilyse Haberman, MD, assistant professor of ophthalmology at NYU Langone. BTW: If you’re really committed to eyelash growth, your next option is to get a prescription for Latisse: the only FDA-approved eyelash serum on the market (more on that in a bit).

How long does it take to see results? 

Even if you use the best of the best eyelash serum and apply it diligently every single day, you have to be patient, since you won’t see results immediately. “Lash serums take time to show any results, so get into the habit of applying one each morning,” says Courtney Buhler, founder and CEO of Sugarlash ProR. And, depending on how your body reacts to the serum, your timeline will vary—some may see results after a month, and others might not notice a difference until month three or four (or if you’re using the wrong formula, never). Are eyelash serums safe? 

As with any product you put on your face—or near your eyeballs—it’s always smart to check in with your doctor before trying it. Pay attention to how your skin and eyes react to the formula—if you notice any redness or irritation, stop using it and consult a physician (you’ve only got one set of eyes, after all). And, now, what you really came here for: Keep reading to search out the seventeen best cilium serums, together with the sole prescription-strength formula, an inexpensive (but effective!) chemist’s shop option, and more.