You don’t need to have had lash extensions to use a lash serum regularly, of course. In fact, ever since I started using a lash serum regularly, I opt for lash extensions less and less. But that also doesn’t mean that every lash serum out there is going to give you the Bambi lashes of your dreams. So, we tapped Dendy Engelman, M.D., FACMS, FAAD, board-certified cosmetic dermatologist and Mohs surgeon at Shafer Clinic in New York City, to break down exactly what you should be looking for in an effective lash growth serum.

Do lash growth serums really work?

Truth be told, the term lash growth serum is a tad misleading because the only FDA-approved treatment for lash growth is Latisse. If you really want something proven effective for growth and thickness, you can talk to your dermatologist or doctor about getting a prescription (which Latisse needs). If you’re not ready to make a prescription-level commitment, no worries—that doesn’t mean there’s no point in using an OTC option. Most OTC lash serums rely on a long list of moisturizing ingredients and/or follicle-stimulating peptides to leave your lashes stronger and more conditioned—and subsequently looking darker and fuller—or a comparable growth ingredient to bimatoprost (available in prescription Latisse), such as isopropyl cloprostenate. According to Dr. Engelman, some lash serums do work, while others might not be as effective—it’s really all about doing your research and choosing the one that has the ingredient list and formulation to back up their claims. “Most of the lash serums that work have a prostaglandin derivative in them that elongates the anagen (growth) phase of the lash,” explains Dr. Engleman. “As we age, our hair naturally tends to get thinner and drier, and hair loss becomes more common. While we tend to worry most about this happening on our heads, the reality is that it affects our lashes and eyebrows as well.” Nutrients like protein, iron, zinc, and vitamin B12 are vital for healthy hair and growth, so by supplementing these nutrients, lash serums can help extend hair growth and keep the hair healthier and stronger. “Targeting and extending the anagen growth phase of the lashes (the first phase of growth, in which lashes are actively growing) is an important need of an effective lash growth serum,” says Dr. Engelman.

What are the ingredients in lash growth serums that make them effective?

The ingredients in eyelash serums do many things—they serve to supplement the hair with what it needs to grow effectively, condition from root to tip, and add shine in order to help lashes appear overall longer and fuller. “There are natural lash serums, which of course use only natural ingredients, and serums that are not 100% natural, which contain lab-made ingredients,” says Dr. Engelman. Amino acids and peptides are important actives to look for in an eyelash serum. “Two or more amino acids together form a peptide, which is a key component of most lash serums because peptides repair damage to the hair protein and strengthen and improve the appearance of lashes,” explains Dr. Engelman. Vitamin B, or biotin, is also heavily used in lash serums. “Keratin is a protein that serves as a building block for strong, healthy hair (including lashes), and vitamin B/biotin is known to strengthen the keratin in lash hairs,” says Dr. Engelman. Other natural ingredients commonly found in lash growth serums are rosemary, castor oil, and olive oil. “Castor oil contains ricinoleic acid, which is antimicrobial, detoxifying, and moisturizing to the follicle,” says Dr. Engelman. “Both castor oil and olive oil can help strengthen the hairs and add shine, which gives lashes the appearance of being fuller.”

What should you look for in a lash growth serum?

You want to look for ingredients that are designed to target the health of the follicle and the strength and appearance of the lashes themselves. “As mentioned before, extending the anagen (first growth) phase of eyelash growth is important, and something to look out for in a truly effective formula,” says Dr. Engelman. “Amino acids/peptides are common in lash serums and are great for improving the strength and growth of lashes. Conditioning agents are also great to look for, as they keep the skin and hair moisturized, and contribute to fuller-looking lashes.” Make your search for the best lash growth serum a little easier with a curated list, below.