This Nail Serum Gave Us Visibly Stronger Nails In Just 7 Days

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When hair is weak, brittle, and breaking, beauty experts advise reaching for bond-building treatments, especially for those who tend to bleach, color, or heat-style their hair. It makes sense: Bonds make up our hair’s structure, so healthy bonds mean healthy, shiny hair. So, why not apply the same kind of science to other parts of our body? Namely, parts that also go through a lot of damage, like our nails — they’re buffed and polished, scraped and picked at, and blasted with UV light. Even if you’re not a manicure kind of person, there’s still all that hand-washing and nail-biting and chemical cleaning products to content with.

This is exactly the thinking behind OPI’s latest offering: The Repair Mode Serum, which has already taken social media by storm with its seemingly magical nail-strengthening and soothing abilities. But there’s no magic here, just all that good, honest bond-building science. Repair Mode uses something called “Ulti-Plex technology," a patented secret ingredient that penetrates the nail to build new keratin bonds (the protein that our nails are made from). Rather than just hydrate and nourish on a surface level, the serum strengthens nails from within, making them feel and look stronger and smoother, with fewer ridges, less discoloration, and more resistance to breakage or peeling.

It does all sound too good to be true, so we rounded up three R29 editors with weak nails to put Repair Mode to the test. Two members tested it out over a week — the time frame OPI claims you’ll see improvements by — and one for a whole month. Read on for their thoughts.

“Months of back-to-back BIAB or Builder in a Bottle nails (it’s important to take breaks!) meant my nails were worse for wear when I picked up this bonding serum. I’d never known them to be more weak, brittle, or stained. I even struggled to do everyday things — like wash my hair — because they were so sensitive. In other words, this product came at the right time.”

“The formula itself is clear and unassuming; it looks just like water. I wasn’t too taken by the smell of alcohol, but OPI’s promise of smoother, stronger nails in just under a week convinced me to keep going. Miraculously, after seven days, my nails weren't as sensitive or dented (a result of e-files), and I could finally do everyday tasks without wincing, but the best results have been thanks to continued use.”

“I’ve since been applying this nail serum once a day followed by a heavy helping of cuticle oil (at night before bed) to moisturize the skin and nail plate, and it’s like none of the damage ever happened. As you can probably see in the before and after photos, my nails have grown well and the tips no longer feel like paper. Manicurists I’ve spoken to extol the virtues of cuticle oil in particular for healthy nail growth, so if you’re going to use this serum, I’d recommend following with a slick of oil, too. If you’d rather spend nothing and you happen to have vegetable oil in your kitchen, London-based podiatrist Dina Gohil once told me it's a great, cheap alternative for preventing nail splits, boosting hydration, and smoothing the texture of nails.”

“My nails aren’t disastrous, but they’re not great either — they’re naturally quite ridged, plus they’re a bit cracked and bendy. That’s probably unsurprising given that my nail-care routine is nonexistent, aside from doing a DIY shellac (a habit I picked up out of necessity in lockdown that just kind of stuck) and then guiltily peeling it off two weeks later. I also have the rather charming habit of picking at my cuticles (they’ve made even the most emotionally robust of manicurists weep), but addressing my somewhat anxious energy might be beyond the remit of a mere nail serum.”

“Given my low-effort habits, I did worry that this might be a bit of a waste of time, but I was pleasantly surprised: Keeping my bottle next to my toothbrush as a reminder to apply every day really helped (you need to apply twice a day), and it’s no big deal if you’re a bit imprecise with the application. It’s also super light and quick drying, and while it does smell slightly of alcohol, it’s pretty inoffensive. I started noticing a difference about four days in: Based on a very unscientific pressing method, my nails felt stronger and less bendy, and they looked a bit smoother, too.

Apparently you can use this serum while you’ve got polish on, but it is more effective on bare nails (makes sense). For me, this would definitely be the main hurdle for using it on any kind of regular basis — I’m not sure the results are worth having to take a break from my basically permanent black nails. That said, I’d definitely keep it on hand for those moments when I felt like my nails needed an emergency overhaul.”

“My mum always says to me that her nails are only ever strong when she’s in the sun or pregnant. Mine are consistently weak, layering on top of themselves and snapping off, so I assume I inherited this wonderful weak-nailed gene. My main thing I want to try and solve is the nail peeling and being able to keep them long for longer as they normally snap off or bend pretty quickly without wearing a strengthener.”

“The Repaid Mode serum was much different than I imagined; it almost feels like you are hardly putting anything on. I guessed it would be a thick gel or oil, but it is actually a very watery consistency that dries almost immediately which I like and, personally, I hardly noticed any smell. After seven days of using two times a day, I do surprisingly feel like I’ve noticed a difference. While my peeling hasn’t completely gone away and there wasn’t a ton of visual improvement, I do feel like my nails are stronger and less fragile and that they were able to grow longer without cracking off immediately. I will definitely continue using it daily, as I feel like although it doesn’t give them a shine, it’s much more important to me that they stay strong and healthy than look pretty, so it’s a win for me.”