Latisse was originally a glaucoma medication. Its active ingredient, bimatoprost, was first approved by the FDA in 2001 as a prescription eye drop to lower pressure inside the eye for people with open-angle glaucoma or ocular hypertension. Doctors and patients noticed an unexpected bonus: the drug made eyelashes grow longer, fuller, and darker. That side effect eventually became the main attraction.
How a Glaucoma Drug Became a Beauty Product
Bimatoprost was developed to treat two related conditions. Open-angle glaucoma is a disease where fluid pressure builds up inside the eye and gradually damages the optic nerve, potentially leading to vision loss. Ocular hypertension is elevated eye pressure that hasn’t yet caused nerve damage but raises the risk of glaucoma developing. A single drop of bimatoprost in the affected eye each evening lowers that pressure effectively.
But patients using the eye drops kept reporting the same curious side effect: their eyelashes were growing noticeably longer and thicker. Allergan, the company behind the glaucoma product (sold as Lumigan), recognized the cosmetic potential and pursued clinical trials specifically focused on eyelash growth. The FDA approved the repackaged product as Latisse in 2008, making it the first and only prescription treatment for hypotrichosis of the eyelashes, the clinical term for having inadequate or sparse lashes.
Both Lumigan and Latisse contain bimatoprost at a 0.03% concentration. The difference is how they’re applied. Lumigan is dropped directly into the eye to treat glaucoma. Latisse is brushed along the upper lash line with a sterile applicator, so the drug reaches the hair follicles at the base of the lashes rather than flooding the eye itself.
Why Bimatoprost Makes Lashes Grow
Bimatoprost is a synthetic compound modeled after naturally occurring fatty acid molecules called prostaglandins. Hair follicles have receptors for prostaglandins on their surface, and when bimatoprost binds to those receptors, it shifts the hair growth cycle. Specifically, it pushes more lash follicles into the active growth phase (called anagen) and keeps them there longer than usual. It also enlarges the hair bulb at the base of each follicle, which produces a thicker strand.
The combined result is lashes that are longer, denser, and darker. These changes don’t happen overnight. In clinical trials, lashes were measurably longer by week 4, but fullness and darkness took until about week 8 to become noticeable. Full results appeared at 16 weeks.
What the Clinical Trials Showed
Allergan’s pivotal U.S. trial enrolled 278 participants and compared Latisse against a placebo solution applied the same way. By the 16-week mark, the Latisse group saw dramatic changes measured through digital image analysis: lashes were 106% fuller, 25% longer, and 18% darker compared to baseline. Those numbers explain why the product generated so much buzz. A doubling in fullness is visible in a mirror without any measuring tools.
The effects are not permanent. If you stop using Latisse, your lashes gradually return to their original appearance over a period of weeks to months as the growth cycle resets to its natural rhythm.
Side Effects Worth Knowing About
Because Latisse contains the same active ingredient used in glaucoma drops, it carries some of the same risks, though the way it’s applied matters. The most discussed concern is iris color change, specifically a darkening of the colored part of the eye. When bimatoprost is dropped directly into the eye for glaucoma treatment, a small number of patients with lighter, mixed-color eyes (particularly hazel) have experienced their irises turning more brown. However, no cases of iris color change have been reported in U.S. patients using Latisse as directed along the lash line, likely because far less medication enters the eye with topical application.
A more common and well-documented issue is something called prostaglandin-associated periorbitopathy, a cluster of changes around the eye socket. This has been reported in more than 10% of patients treated with bimatoprost. The drug can inhibit fat cell development in the tissue surrounding the eye, which may lead to a sunken appearance of the upper eyelid, a deepening of the crease above the eye, thinning of the fat pads below the eye, or darkening of the skin around the eyelids. Some people also notice mild drooping of the upper lid.
These changes tend to develop gradually with long-term use and can be subtle enough that users attribute them to aging rather than the product. They are generally reversible after stopping treatment, though recovery can take time as the orbital fat slowly rebuilds.
From Side Effect to Standalone Product
Latisse is one of the more notable examples in pharmaceutical history of a side effect becoming a product in its own right. The biology that made it useful for glaucoma, its ability to interact with prostaglandin receptors, turned out to have a completely separate cosmetic application that neither the manufacturer nor researchers originally intended. The same 0.03% bimatoprost solution serves two very different purposes depending on where you put it: inside the eye to protect vision, or along the lash line to enhance appearance.