Many of the most popular eyelash growth serums contain prostaglandin analogs, synthetic compounds that mimic naturally occurring prostaglandins in your body. These ingredients are what make lash serums actually work to lengthen lashes, but they also carry side effects worth understanding before you buy. The tricky part: these compounds appear under a long list of chemical names that are easy to miss on a label.
How Prostaglandins Make Lashes Grow
Prostaglandin analogs stimulate lash growth by extending the active growth phase of each hair follicle and pushing resting follicles back into growth mode. The result is lashes that grow longer before they naturally shed, and more follicles producing lashes at any given time. This is the same mechanism behind the prescription glaucoma eye drops that first tipped researchers off to lash growth as a “side effect.”
Brands That Contain Prostaglandin Analogs
The most common prostaglandin analog in over-the-counter lash serums is isopropyl cloprostenate. Unlike bimatoprost (the active ingredient in prescription Latisse), isopropyl cloprostenate is not FDA-approved for lash growth. It shows up in a wide range of products, including several bestsellers:
- GrandeLash MD (Grande Cosmetics)
- Lash Boost (Rodan + Fields)
- Babe Lash Eyelash Growth Serum and Essential Serum
- RapidLash Eyelash Enhancing Serum
- neuLASH Lash Enhancing Serum
- UKLash Eyelash Serum
- Borboleta Lash Serum
- Lilly Lashes Level Up Lash Enhancing Serum
- Panthrix Eyelash Activating Serum
Latisse remains the only FDA-approved lash growth product. It contains bimatoprost at 0.03% and requires a prescription.
Names to Look for on Ingredient Labels
Prostaglandin analogs rarely appear under the word “prostaglandin” on a product label. The European Commission has cataloged over a dozen synthetic prostaglandin analogs used in cosmetics, and many have names that look like gibberish to a non-chemist. Here are the ones you’re most likely to encounter:
- Isopropyl cloprostenate (the most common in OTC serums)
- Bimatoprost (prescription only, found in Latisse)
- Ethyl tafluprostamide
- Dechloro ethylcloprostenolamide
- Ethyl travoprostamide
- Dehydrolatanoprost
- Norbimatoprost
- Trifluoromethyl dehydrolatanoprost
Additional variants include cyclopropylbimatoprost, dechloro cyclopropylcloprostenolamide, and dihydroxypropyl dehydrolatanoprostamide. If any ingredient name contains “prost,” “prostamide,” or “prostenate,” it is almost certainly a prostaglandin analog.
Side Effects to Be Aware Of
Prostaglandin analogs are effective, but they come with a specific set of risks that go beyond typical cosmetic irritation.
Changes Around the Eyes
The most discussed side effect is prostaglandin-associated periorbitopathy, a collection of changes to the tissue surrounding your eyes. These include fat loss around the eye socket, a sunken or hollowed appearance, deeper upper eyelid creases, and darkening of the skin on and around the eyelids. In studies of glaucoma patients using prostaglandin drops daily, the incidence of deepening of the upper eyelid crease ranged from 25% to 60%, with bimatoprost users at the higher end. The mechanism involves the prostaglandin receptor triggering fat breakdown and blocking new fat cell formation in the orbital area.
These changes generally develop after at least three months of consistent use. The good news is that fat loss and skin darkening around the eyes are considered reversible once you stop using the product, though full reversal can take months.
Iris Color Changes
Bimatoprost can increase brown pigmentation in the iris. In clinical trials, about 1.5% of patients using bimatoprost once daily for 12 months developed noticeable iris darkening. This is most relevant for people with mixed-color eyes (hazel, green-brown, blue-brown), where the brown pigment can spread. This change is likely permanent. It does not progress further after you stop treatment, but it does not reverse either. While 1.5% is a low number, permanence makes it worth considering, especially if you have light or multicolored eyes.
The Regulatory Gray Area
Latisse went through the FDA approval process as a drug, which means its safety profile has been formally studied and documented. Over-the-counter lash serums containing isopropyl cloprostenate and other analogs exist in a gray area. They are marketed as cosmetics, not drugs, which means they do not go through the same approval process. The American Academy of Ophthalmology has specifically noted that isopropyl cloprostenate is not FDA-approved. The FDA has issued warning letters to companies making drug-like growth claims for cosmetic lash products, though enforcement has been limited.
This does not necessarily mean OTC serums are unsafe. It means the safety data is thinner, and the concentrations of prostaglandin analogs in these products are not standardized or publicly disclosed the way prescription drug formulations are.
Prostaglandin-Free Alternatives
If you want to avoid prostaglandins entirely, look for serums built around peptides. Peptides are short chains of amino acids that nourish lash follicles and stimulate keratin production, the structural protein that lashes are made of. One study found that peptide-based formulas produced visibly longer lashes and new eyebrow hair follicle activity after 12 weeks of use. The results are generally more modest than what prostaglandin serums deliver, but the side effect profile is significantly milder.
Other prostaglandin-free ingredients to look for include biotin, castor oil, and various plant extracts. These serums focus more on conditioning and preventing breakage than on altering the growth cycle itself. If a serum’s ingredient list contains no words ending in “prost,” “prostamide,” or “prostenate,” it is prostaglandin-free.