What are the side effects of bimatoprost?

If you’re considering using bimatoprost 0.03% for eyelash growth (or perhaps you’ve already started!) you may be wondering what the side effects are, and how likely you are to experience side effects of bimatoprost.

First of all, thank you for asking!! As a provider of a prescribed medical treatment, we are all about patient empowerment and patients taking their health decisions into their own hands. So that you can make the best decision for you, here’s a bit of info on the potential side effects of using bimatoprost for eyelash growth.

First things first: Bimatoprost is generally regarded as very safe

This is because of the relatively low rate of side effects (see below) observed in research trials. Because bimatoprost is prescribed, it’s subject to wayyyy more scrutiny than your typical cosmetic product, including any of the over-the-counter eyelash serums available. That’s not to say that these alternatives are necessarily unsafe, but rather that they’ve not been studied to such a high standard. Luckily, we do have this data for bimatoprost (which is why we’re so excited about offering it to you).

Side effects of bimatoprost for eyelash growth are relatively rare

If you’ve ever read the information leaflet on a prescription medication, you’ll know that no medication is without risks. But you could say the same about going for a drive or eating fish at a restaurant, right? It’s really just about a risk assessment, but we can understand that the warnings on prescription leaflets can be daunting.

Here’s a quick stat to ease your concerns: In a 278-patient trial on the use of bimatoprost for eyelash growth, the most common side effects occurred in less than 4% of participants.[1] That’s just 1 in every 25 people in the trial... meaning the other 24 used the treatment side effect-free.

Here’s hoping you’re not that 1 in 25, but in case you are, next we’ll explain what those side effects could be.

What are the side effects of bimatoprost?

Here are the most common side effects observed in clinical trials of bimatoprost for eyelash growth (ie applied along the upper lash line, not inside the eye as it would be used for glaucoma patients):

• Itching and/or redness of the eye (about 4% of people, often resolves after the first few weeks of use)
• Redness of the eyelid (again, tends to go away in a couple of weeks)
• Darkening of the eyelid

It’s worth noting that many of these side effects were not observed at significantly higher rates in the two treatment groups[1]—suggesting that they may be a result of the other ingredients in the formulation, rather than bimatoprost itself.

Generally, these side effects were not severe enough to cease treatment in research trials.

The other main side effect that gets a lot of attention is eye colour change, which we’ll cover below.

What should I do if I experience side effects of bimatoprost?

If you’re experiencing any of the above side effects, or anything else you think might be related to bimatoprost, it’s best to see your healthcare provider. 

Can bimatoprost change my eye colour?

There is a lot of worry around the potential for bimatoprost to darken eye colour, but equally a load of myths to debunk around the topic. Here’s our 2p.

As a quick background, bimatoprost can stimulate the production of melanin—the stuff that makes us tan, but that is also responsible for pigmentation in our hair and eyes. If bimatoprost comes into direct contact with the iris of the eye (the coloured part), it can cause the overproduction of melanin, and thus lead to slight darkening of the eyes. 

This has been observed in research trials on Lumigan®, the brand-name version of bimatoprost used in patients with glaucoma. Lumigan® is applied directly to the eye as eye drops, so there is significantly more contact between the eye and the solution than in application to the upper lash line. In research on Lumigan, only about 1-2% of patients experience eye colour changes.

A small amount of eye darkening has been observed mostly in patients with green and hazel eyes. This change is less common in patients with blue eyes, whose eyes have fewer pigment-inducing cells.

While eye colour changes can seem scary, it’s important to remember that bimatoprost for eyelash growth is applied directly to the lash line, not inside of the eye like Lumigan—so the chances of any liquid even touching your eyes, let alone resulting in eye colour change, is low.

[1] https://pubmed.ncbi.nlm.nih.gov/23873891/