Kerasal improves the appearance of fungal toenails, but it does not kill the fungus itself. Its two active ingredients, urea and salicylic acid, work by softening and peeling away damaged nail tissue rather than targeting the infection underneath. In a clinical study of 65 patients with toenail fungus, 85% saw visible improvement in nail appearance after four weeks of use. That’s a meaningful cosmetic result, but it’s not the same as curing the infection.
What Kerasal Actually Does
Kerasal is classified as a keratolytic, not an antifungal. Salicylic acid causes the outer layers of thickened nail to shed, while urea softens and moisturizes the remaining nail plate. Together, they break down the dense, discolored keratin that makes a fungal nail look so rough. The nail becomes thinner, smoother, and closer to its normal color, which is why so many users feel it’s “working” within the first week or two.
In the clinical trial, 65% of patients reported improvement after just one week, and 82% saw results by two weeks. These numbers reflect how the nail looks, not whether the fungus is gone. The study measured appearance on a four-point scale and did not test whether the underlying fungal organism was eliminated. So while the nail may look dramatically better, the infection can still be present and spreading beneath the surface.
It’s worth noting that Kerasal does make a separate product for athlete’s foot that contains tolnaftate, an actual antifungal. But the label on that product specifically states it is “not effective on the scalp or nails.” The nail repair formula and the athlete’s foot formula are not interchangeable.
Why It Pairs Well With Antifungal Treatment
Where Kerasal becomes genuinely useful is as a companion to actual antifungal medication. Toenails are made of tightly packed keratin fibers, and that dense structure makes it hard for topical antifungals to reach the nail bed where the fungus lives. Urea and salicylic acid loosen that structure by denaturing the keratin and increasing pore size within the nail plate. Research on nail penetration has shown that pretreating nails with keratolytic agents can improve drug permeability by several fold, with one study finding up to an 18-fold increase in how well a common prescription antifungal moved through the nail.
In practical terms, this means applying Kerasal before or alongside a prescription or over-the-counter antifungal can help that medication actually reach the infection. Podiatrists sometimes recommend this approach: use Kerasal to thin and soften the nail, then apply an antifungal so it penetrates deeper. The cosmetic improvement from Kerasal also helps patients stay motivated during treatment, which matters because toenail fungus takes months to fully resolve.
How to Apply It
The manufacturer recommends applying a thin layer to the affected nail and under the free edge twice daily for the first week, morning and evening. After that initial week, you drop to once daily for at least eight weeks. Depending on how severe the damage is, a full course can take three to six months, roughly the time it takes for a toenail to grow out completely.
Let the product dry for a few minutes before putting on socks or shoes. Consistency matters here. Because Kerasal works by gradually peeling away layers of damaged nail, skipping applications slows the process considerably.
Side Effects to Watch For
Kerasal is generally well tolerated, but salicylic acid can cause mild stinging, dryness, or peeling of the skin around the nail. This is more likely if the surrounding skin is already cracked or irritated, which is common with toenail fungus. Applying the product carefully to the nail itself, rather than flooding the skin around it, reduces the chance of irritation.
Avoid layering Kerasal with other peeling agents or alcohol-based products on the same area. Combining multiple keratolytics can cause moderate to severe skin irritation, redness, and inflammation. If the skin around your nail becomes raw or significantly inflamed, stop use and let it heal before restarting.
Kerasal Alone vs. a Complete Treatment Plan
If your only goal is to make a mildly discolored nail look better for sandal season, Kerasal on its own can deliver noticeable results within a couple of weeks. But if you have a confirmed fungal infection, especially one affecting more than a quarter of the nail, Kerasal alone will not resolve it. The fungus will continue to grow, and the nail will eventually return to its damaged state once you stop applying the product.
Over-the-counter antifungals like tolnaftate and clotrimazole are widely available but have limited success on nails because of the penetration problem described above. Prescription options, whether topical or oral, tend to be more effective. Oral antifungals have the highest cure rates for toenail fungus, typically around 60 to 80%, because they reach the nail bed through the bloodstream rather than trying to soak through from the outside. Topical prescriptions work best for mild to moderate cases.
Using Kerasal as the first step in your routine, softening and thinning the nail before applying whatever antifungal you’re using, gives you the best of both worlds: a better-looking nail during treatment and a better chance that the medication reaches where it needs to go.