Most lash serums are safe for healthy eyes when used as directed. Serums with prostaglandin analogs work best but carry the most risk: irritation, darker eyelid skin, and rarely a permanent change in iris color. Peptide-based serums are gentler but give subtler results. Avoid prostaglandin serums if you're pregnant or breastfeeding, have an eye condition, or take glaucoma medication, and patch test any serum before first use.
1. How eyelashes grow
Each lash goes through three phases. In the growth phase (anagen), which lasts about 30 to 45 days, the lash gets longer. In the transition phase (catagen), growth stops. In the resting phase (telogen), which can last several months, the lash stays in place until it falls out and a new one starts.
Your lashes are all at different stages, which is why a few fall out every day. Serums that work extend the growth phase or strengthen lashes so fewer break early. Either way, you need at least one full cycle, around 12 weeks, to see what a serum can do.
2. The three types of lash serum
3. Known side effects
These effects are mainly linked to prostaglandin analogs. Peptide serums can still cause irritation or allergic reactions to preservatives or fragrance.
Itching, redness or dry eyes
The most common reaction. Usually mild and short-lived. Stop if it lasts more than a few days.
Darkening of eyelid skin
A brown tint along the lash line. Usually fades within weeks to months after stopping.
Iris color change
Rare, more likely with hazel, green or blue eyes, and may be permanent. It's reported mostly with prostaglandin eye drops, which reach the iris more directly than lash-line application.
Hollowing around the eyes
Known as prostaglandin-associated periorbitopathy: loss of fat around the eye with long-term use, which can make eyes look sunken.
Unwanted hair growth
Fine hairs can grow where serum repeatedly touches skin. Wipe away any excess product.
4. Who should avoid lash serums
Talk to an eye doctor before using a prostaglandin serum if any of these apply:
- You are pregnant, trying to conceive, or breastfeeding
- You use glaucoma eye drops; combining them can reduce how well the drops work
- You have uveitis, conjunctivitis, blepharitis or another eye inflammation
- You had eye surgery recently, including LASIK or cataract surgery
- You have light-colored irises and want to avoid any pigment risk
5. How the FDA treats lash serums in the US
Only one product has FDA approval to grow eyelashes: bimatoprost ophthalmic solution 0.03%, approved in 2008 for hypotrichosis (inadequate lashes). It needs a prescription.
Serums you buy at Sephora, Ulta, Amazon or drugstores are sold as cosmetics. Cosmetics don't need FDA approval before sale. Under FDA rules, a product that claims to change how the body works, such as "grows lashes", counts as a drug, which is why many brands say "the look of longer lashes" instead. The Modernization of Cosmetics Regulation Act of 2022 (MoCRA) added requirements for safety substantiation, adverse event reporting and facility registration.
6. How to read a lash serum label
If any of these names appear in the ingredient list, the serum contains a prostaglandin analog:
Common prostaglandin-free actives include myristoyl pentapeptide-17, myristoyl hexapeptide-16, biotin, panthenol, keratin and red clover extract.
7. How to patch test a lash serum
- Apply a small amount behind your ear or on your inner forearm.
- Wait 24 to 48 hours without washing the area.
- If there's no redness or itching, apply to the upper lash line of one eye for three nights.
- If both eyes feel normal after three nights, start regular use.
8. Frequently asked questions
Are prostaglandin-free lash serums safe?
Peptide and conditioning serums have a much lower risk of side effects. Irritation or allergy to other ingredients is still possible, so patch test first.
Is lash serum iris darkening permanent?
Iris color change linked to prostaglandin analogs may be permanent. Eyelid skin darkening usually fades after stopping.
Are lash serums FDA approved?
Only prescription bimatoprost 0.03% is FDA-approved to grow eyelashes. Over-the-counter lash serums are sold as cosmetics and are not FDA-approved.
Can I use a lash serum with lash extensions or a lift?
Oil-free serums are generally compatible with extensions. After a lash lift, wait 24 to 48 hours before applying.