Do nail strengtheners work? Yes, but only the ones that absorb into the nail. The ones that coat the surface feel like they're doing something for a few days, then chip off and take a layer of nail with them. That's the short answer. The longer one is below, with the actual lab data, the science, and what to look for if you want a treatment that holds up over weeks rather than minutes.
Most articles on this question hedge. They quote a dermatologist, list some ingredients, and tell you it depends. The reason is simple: most products on the market don't have data behind them, so writers default to vague advice. A small number of strengtheners have been put through controlled lab testing, and the difference between those and the rest is significant. Here's how to tell them apart.
The Honest Answer: Some Work, Most Don't
If you're looking for a nail strengthener that actually works, the question to ask isn't "does this brand work?" It's "what does this product physically do to my nail?" There are two mechanisms, and only one of them produces structural change to the actual nail.
The first mechanism is coating. Polish-style strengtheners sit on top of the nail and create a hard surface that is adhered to the underlying nail. Brands like OPI Nail Envy, Sally Hansen Hard as Nails, and Revitanail work this way. The nail feels firmer because a layer of resin is sitting on it. The underlying nail is the same. When nail polish chips off, it takes a thin layer of nail away with it, so further thinning and damaging the underlying nail. Solvent-based removal also does harm by dehydrating the nail and removing important protective lipids. You end up where you started, or worse.
The second mechanism is absorption. A small number of products, mostly creams and brush-on treatments, contain protein-based ingredients designed to penetrate the nail and reinforce its structure from within. Hydrolysed keratin is the main active in this category. When applied consistently, it cross-links with the keratin already in your nails, strengthening the bonds that hold the nail layers together. Mavala Scientifique and Dr Tom Nailcare both use absorption-based formulas. CND RescueRXx is positioned as a treatment too, with a keratin-jojoba blend.
This distinction matters because only one of these mechanisms has lab data behind it. Coating-based products report customer testimonials. Absorption-based products can be tested for actual structural change in the nail, because the nail itself is what's changing.
What Hydrolysed Keratin Actually Does
Your nails are keratin. Specifically, they're tightly packed layers of keratin protein arranged in sheets. When nails get weak, those sheets become disorganised, dehydrated, or thinned. The peeling, splitting, and breaking you see is what happens when those layers come apart.
Hydrolysed keratin is keratin that's been broken down into smaller protein fragments, small enough to absorb into the nail rather than sit on the surface. Once inside the nail plate, if these proteins consist of the correct amino acids, they cross-link the existing keratin fibres, reinforcing the bonds between layers. The nail gets stronger from within rather than because something hard is sitting on top of it.
This is why absorption matters so much. A coating can make the nail feel firm, but it can't change the underlying structure. The moment the coating wears off, you're back to the same nail you started with. Hydrolysed keratin actually rebuilds.
Hydration also matters. Nails that lack moisture become brittle and prone to snapping. Nails with too much moisture bend and tear. The ideal nail is flexible but firm, which is why effective strengtheners restore hydration alongside reinforcing structure. A treatment that delivers protein and moisture into the nail has a measurable effect, particularly over weeks of consistent use. A surface coating doesn't.
The catch is that absorption takes time. You won't see results in 24 hours. Most absorption-based treatments take 10 to 14 days for noticeable change. Damaged nails can take several weeks to reach their best by maximally reinforcing the keratin fibres. That's not a flaw, it's how nail structure works. The visible nail plate is dead keratin pushed forward from the matrix, so the nail will not reach its very best until any damaged area has grown out, and has been replaced by maximally reinforced new nail. Coatings feel faster because they work cosmetically. Absorption is slower because it's working structurally.
What to Look For in a Nail Strengthener
A few specific things separate strengtheners that work from strengtheners that don't.
Look for actual lab data, not testimonials. Customer testimonials and "visibly stronger nails" claims are everywhere. Controlled lab testing with specific percentages and methodology is rare. Pharmacy-stocked brands like OPI, Sally Hansen, and Revitanail rely on customer-reported results without publishing controlled lab studies. Treatment-focused brands like Dr Tom Nailcare publish lab results with exact figures. If a brand can't tell you how much stronger nails got, by what percentage, in how many days, they probably don't know.
Check whether the formula absorbs or coats. Polish-based strengtheners like OPI Nail Envy, Sally Hansen Hard as Nails, and Revitanail use coatings. Cream-based and serum-style treatments like Dr Tom Nailcare and Mavala Scientifique absorb into the nail. Both have their place. If you want a temporary cosmetic effect for a few days, a coating works. If you want structural change, absorption is the approach with the evidence.
Avoid the harsh chemicals. Carcinogens such as formaldehyde, along with toluene and DBP, appear in some strengtheners and can damage the nail plate over time. Many natural and treatment-based formulas avoid these entirely. Read the ingredient list before you buy. Revitanail Original contains formaldehyde; their Sensitive Nail Strengthener doesn't. OPI varies by formulation. Dr Tom Nailcare contains none.
Match the product to your problem. Brittle and weak nails respond well to absorption-based treatments like Mavala Scientifique or Dr Tom Nailcare, which rebuild structure over weeks of use. Gel-damaged nails need rebuilding without further chemical exposure, which the same approach delivers. For people who want a polish-style option, OPI Nail Envy and Sally Hansen Hard as Nails offer surface coatings, though they don't change the underlying nail. The best product for one issue isn't always the best for another, so be specific about what you're trying to fix before you buy.
What Dr Tom Nailcare Did Differently
Dr Tom Cawood is a hospital doctor, published lab scientist with 40+ peer-reviewed papers, and passionate classical guitarist. The reason he built a nail strengthener is that he kept breaking nails. Classical guitar demands precise, well-shaped natural nails on the right hand. Every snap meant weeks without playing. He'd tried existing strengtheners and they didn't hold up.
So he did what scientists do. He looked at how nail strength was being tested, found the existing methods inadequate, and built a new one. Their novel lab model uses New Zealand sheep's wool keratin to create lab nails which can then be tested to breaking point. These lab nails were used as an indicative material to demonstrate how human nails are likely to perform. This lab model was a world-first that allowed them to test various active ingredients and create an optimal formulation before then going on to consumer studies.
The formula uses hydrolysed New Zealand wool keratin, processed to contain the correct blend of amino acids to optimise keratin fibre cross-linking. It absorbs into the nail and reinforces it from within by cross-linking the keratin fibres in your nail. The full formula contains other active ingredients, which together with the hydrolysed keratin works to restore hydration, reinforce nail structure, increase resilience, and improve structural strength. No formaldehyde, no nitrocellulose, no toxic trio chemicals.
Lab testing showed the cream made lab nails 30% stronger in 10 days. The combination treatment of cream plus liquid made lab nails 78% stronger in 2 weeks. Consumer testing was run separately, and included classical guitarists who are very demanding of their nails. With the cream, 95% of users reported stronger, healthier, more flexible nails. With the combination treatment, 100% of users reported stronger, healthier nails.
Dr Tom Nailcare backs the combination treatment with a performance promise. If you don't see benefits after consistent use, you get 100% of your money back (currently available in New Zealand and Australia). For best results, use consistently. Daily application strengthens nails over time.
Frequently Asked Questions
How long does it take for a nail strengthener to work? Absorption-based treatments take 10 to 14 days for visible improvement, and 4 to 6 weeks for fully rebuilt nails as they grow out. Coating-based products feel hard immediately because of the surface layer, but they don't change the nail underneath. If you want longer-lasting results rather than an overnight effect, absorption is the right approach and consistency is the requirement.
Can nail strengtheners repair gel or acrylic damage? Absorption-based treatments are well-suited to recovering from gel or acrylic damage because they rebuild the nail from within rather than adding more chemical exposure. Surface coatings can make damaged nails feel firmer for a few days, but they don't address the underlying weakness and the removal process can do further harm. Look for a cream or brush-on treatment with hydrolysed keratin, applied daily, and expect 4 to 6 weeks for nails to fully recover.
Are natural nail strengtheners as effective as chemical ones? When properly formulated and lab-tested, natural ingredients like keratin can match or outperform synthetic formulas. The difference isn't natural versus chemical, it's tested versus untested. A natural formula without evidence is no more credible than a synthetic one. Look for brands that publish controlled lab data with specific percentages.
Do I need to keep using a nail strengthener forever? No. Once nails reach a strong, healthy state, most people scale back to maintenance use a few times a week rather than stopping entirely. The exact pattern depends on your nail type, lifestyle, and what damaged the nails in the first place. People who use gel polish or do hand-intensive work usually need ongoing maintenance. People who are able to reduce the on-going damage to their nails often see longer-lasting improvement and can taper off.
Can nail strengtheners replace polish? For strengthening purposes, yes. Polish is decorative; a treatment-based strengthener does the structural work. You don't need polish to have strong nails. If you do want to wear polish for the look, a cream-based strengthener can be applied underneath at night, since it absorbs while you sleep without leaving any residue or interfering with what goes on top. But frequent application and removal of nail-polish products are likely to weaken your underlying nail, and prolonged use may set up a cycle of requiring to use such products because the underlying nail is so weak.
See the Difference
If you want a nail strengthener with lab data behind it rather than testimonials, Dr Tom Nailcare's cream was proven to make lab nails 30% stronger in 10 days, and the combination treatment was proven to make lab nails 78% stronger in 2 weeks. Shop Dr Tom Nail Strengtheners and see the real results for yourself. Here's to stronger, healthier nails.