Latisse contains bimatoprost at a concentration of 0.03%, a compound originally developed to treat glaucoma that was later found to make eyelashes grow longer, thicker, and darker. It’s the only FDA-approved prescription treatment for inadequate eyelash growth, and the active ingredient works by extending the natural growth cycle of each lash follicle.
The Active Ingredient: Bimatoprost
Bimatoprost is a synthetic compound that mimics a naturally occurring fatty acid in the body called a prostaglandin. It was first approved by the FDA in 2001 as a glaucoma medication, where it lowers eye pressure by helping fluid drain from the eye. Doctors noticed that patients using bimatoprost eye drops were developing remarkably long, thick eyelashes as a side effect. That observation eventually led to Latisse’s approval specifically for eyelash growth.
At the 0.03% concentration in Latisse, bimatoprost works on hair follicles in two ways. First, it speeds up the transition from the resting phase of the hair cycle to the active growth phase. Second, and more importantly, it extends the duration of that active growth phase. Since eyelash length is determined by how long a follicle stays in active growth before the lash falls out, a longer growth window means a longer lash. Bimatoprost also increases the percentage of lash follicles that are actively growing at any given time, which is why lashes appear thicker overall.
Inactive Ingredients
Beyond bimatoprost, the solution contains several inactive ingredients that keep it stable, sterile, and at the right pH for use near the eyes. The most notable one is benzalkonium chloride, a preservative commonly used in eye drops. Benzalkonium chloride prevents bacterial contamination but has one practical drawback: it can be absorbed by soft contact lenses and discolor them. If you wear contacts, you need to remove them before applying Latisse and wait at least 15 minutes before putting them back in. The remaining inactive ingredients are standard pharmaceutical buffers and stabilizers that maintain the solution’s consistency and shelf life.
How Latisse Is Applied
Latisse is applied once daily at night, using a sterile single-use applicator. You draw the applicator along the skin at the base of your upper eyelashes, moving from the inner corner to the outer corner of the lash line. The solution is meant only for the upper lid margin where lashes meet skin. It should not be applied directly into the eye or onto the lower lashes. Enough solution naturally migrates to the lower lash line through blinking.
Most people start noticing visible changes around 4 weeks. Full results take about 16 weeks of consistent nightly use. If you stop applying Latisse, your lashes gradually return to their original appearance over a period of weeks to months as the hair growth cycle resets.
Side Effects Tied to the Formula
Because bimatoprost is a prostaglandin analog, it carries some side effects specific to that class of compound. The most commonly discussed ones relate to pigmentation changes.
- Skin darkening around the eyes: This occurs in fewer than 4% of users and is completely reversible once you stop using the product.
- Iris color change: In glaucoma patients who apply bimatoprost directly into the eye, permanent darkening of the iris has been observed in 1 to 2% of cases. This has not been seen in clinical trials of Latisse when applied as directed to the eyelid skin, likely because far less of the solution reaches the interior of the eye.
- Eye irritation or redness: This affects a small percentage of users and typically resolves after discontinuing use.
People with certain eye conditions, including conjunctivitis, macular edema, or uveitis, should not use Latisse. Because bimatoprost lowers eye pressure, anyone already using glaucoma medications needs monitoring while using Latisse to avoid an excessive drop in intraocular pressure.
Why It Requires a Prescription
Latisse is a prescription product because bimatoprost is a pharmaceutical compound with real effects on eye physiology. Over-the-counter eyelash serums typically use peptides or conditioning agents that may strengthen existing lashes but don’t alter the hair growth cycle the way bimatoprost does. The 0.03% bimatoprost concentration in Latisse is the same active ingredient found in glaucoma drops, just marketed and packaged differently. That pharmacological potency is what makes it effective, but it’s also why it needs medical oversight.