This Ingredient in Your Favourite Lash Growth Serum Could Be Causing Volume Loss, Dark Circles and Hyperpigmentation

While we've traditionally enhanced our eyelashes with mascara and falsies, there is a growing market for over-the-counter lash growth serums, which promise to lengthen lashes dramatically in just a matter of weeks. The sheer volume of before-and-afters on social media is certainly compelling, and in the last few years, there has been a boom in just how many are available on the market, from heritage brands to TikTok shop suppliers alike.

However, unwanted side effects should encourage caution in shoppers. People have taken to social media to bemoan the effects of such products, including fat loss around the orbital bone, sunken under-eyes, dark circles, hyperpigmentation and increased sensitivity.

The culprit in this case is an ingredient known as prostaglandin analogues (PGAs), explains Professor Jonathan Roos, ophthalmologist and co-founder of FaceRestoration. Although lash growth serums are generally considered safe when used according to packet instructions, some that include this ingredient, come with risks. "In many countries, these serums are classified as cosmetics—meaning they face less regulatory oversight than medicines" explains the doctor. "That’s why you’ll find them in stores and online, even though countries like Sweden and Canada have banned prostaglandin analogues in over-the-counter products." Read on to learn more about the potential side effects, and how to scan the ingredient list of your own serum effectively.

What are prostaglandin analogues?

While not all lash growth serums include prostaglandin analogues, many of the most effective ones do. They are synthetic substances which mirror the effect of prostaglandins, which already exist in the body. Medically, prostaglandin analogues are used to treat eye conditions like glaucoma; however, they also have cosmetic use, primarily encouraging eyelash growth by stimulating the active growth phase of hair follicles.

Can they cause unwanted side-effects?

"Prostaglandin analogues stimulate lash growth by prolonging the growth phase of your lashes—but they also act on surrounding skin and fat," explains Professor Roos. "The same way they reshape eyelid tissues in glaucoma patients, which is where we first noticed these effects, they can also change your appearance even at lower beauty product concentrations, as prostaglandins are inflammatory."

So, what are the side effects? Fat cells around the eyes can shrink, creating volume loss or the appearance of hollowed-out under eyes. People can also experience dark circles due to pigmentation from these pro-inflammatory molecules, or a change in contour from the fat shrinkage, which causes shadows and darkening. Other effects include puffiness, red, dry, itchy or irritated eyes and unwanted hair growth if the serum drips onto nearby skin. In very rare cases, there can be permanent darkening of the iris, particularly in those with lighter eyes and eyelid drooping (pseudo ptosis).

There are some early signs to look out for. These include darker skin at the lash line, puffiness or hollowness under the eyes, and red, itchy or stinging eyes—if you experience these, stop using the product promptly.

Will you always experience side-effects and can they be reversed?

It's worth noting that the majority of these side effects are rare and that not everyone will experience them. However, the doctor adds, "When they happen, especially fat loss and iris darkening, they might be permanent—even after stopping the serum. Most people who notice redness or pigmentation changes see improvement after stopping use. Always err on the side of caution with any product applied close to your eyes. The bottom line: always read ingredients carefully and talk to a healthcare provider before using lash serums with prostaglandin analogues. Gorgeous lashes aren’t worth permanent changes to the eyes and skin."

How can you identify products with prostaglandin analogues?

Professor Roos advises scanning the ingredient for the “-prost” suffix or names like bimatoprost, latanoprost, travoprost, or isopropyl cloprostenate. "If you’re unsure, consult your pharmacist or a qualified eye doctor before using any lash serum. Even over-the-counter serums or products not labelled as pharmaceuticals can contain them. Always read the fine print—don’t rely on marketing alone, as many lash serums rely on prostaglandin for their effect."

What are the alternatives?

"Some serums use peptides or botanical ingredients instead, which don’t come with these side effects—although they may be less dramatic in boosting lash growth," says Professor Roos. "Using mascara or false lashes is another safe choice."