Allantoin has modest scar-softening properties, but the evidence for dramatic scar improvement is limited. Most research tests allantoin as one ingredient in a combination product, making it hard to isolate its individual contribution. What’s clear is that allantoin helps soften and smooth skin, promotes new cell growth, and moisturizes healing tissue. Whether that translates to visibly flattening or fading a scar depends on the scar type, how early you start, and what else is in the product.
What Allantoin Actually Does to Skin
Allantoin is a naturally occurring compound found in plants like comfrey, as well as in snail mucus and certain grains. It works on skin in three main ways that are relevant to scarring.
First, it’s keratolytic. As Cleveland Clinic dermatologist Wilma Bergfeld explains, allantoin softens the proteins in your skin and helps shed dead cells, leaving the surface smoother. For raised scars, this softening action can gradually reduce the tough, fibrous feel of scar tissue. Second, it promotes epithelialization, meaning it encourages your skin to grow new cells over a wound site. Faster, more organized cell turnover can improve how a scar looks as it matures. Third, it acts as a skin protectant and moisturizer, which keeps healing skin hydrated and less prone to cracking or irritation.
The FDA recognizes allantoin as a skin protectant active ingredient at concentrations of 0.5 to 2 percent. Most over-the-counter scar gels, including well-known brands like Mederma, contain allantoin within this range alongside other active ingredients.
The Clinical Evidence for Scars
Here’s where things get complicated. Nearly all clinical studies on allantoin and scars test it in combination with other ingredients, particularly onion extract and heparin (a blood-thinning compound). So the results reflect the full formula, not allantoin alone.
In one observational study of patients who began treatment within three weeks of injury, a gel containing onion extract, heparin, and allantoin produced statistically significant improvements in scar color, pliability, pain, and itching after two to three months of use. Improvements continued through four to five months of treatment. Starting early appeared to matter: patients who began applying the gel soon after wound closure saw better outcomes than those who waited.
A separate clinical study examined an overnight patch containing onion extract, allantoin, and a sugar-based compound on hypertrophic scars and keloids. Ultrasound imaging confirmed significant reductions in scar thickness and blood vessel density after 12 weeks, with continued improvement out to 24 weeks. These are encouraging numbers, but again, allantoin was one of several ingredients.
Not all trials are positive. A randomized, double-blinded trial of 20 patients with raised thyroidectomy scars compared a gel containing onion extract, heparin, and allantoin against a plain glycerine placebo. After six weeks of twice-daily application, the combination gel was not proven superior to placebo on any scar measurement. The short treatment window and small sample size may have played a role, but it’s a reminder that results are inconsistent.
How It Compares to Other Scar Treatments
Silicone sheets and silicone-based gels remain the most studied and broadly recommended topical option for raised scars. They work by trapping moisture against the scar surface and creating a protective barrier. Allantoin-based gels haven’t been shown to outperform silicone in head-to-head comparisons.
That said, allantoin-containing products are widely available, affordable, and well tolerated. Allergic reactions to allantoin itself are rare. Cosmetic contact dermatitis in general accounts for only 2 to 4 percent of dermatology visits, and allantoin is not among the common culprits. For people who find silicone sheets uncomfortable or impractical, an allantoin-based gel is a reasonable alternative, particularly for newer scars that are still maturing.
What to Realistically Expect
If you decide to try an allantoin product on a scar, the research suggests a few practical guidelines. Start as early as possible after the wound has fully closed. Scars are most responsive to topical treatment in their first few months, when collagen is still being actively remodeled. Apply the product consistently, at least twice daily, for a minimum of two to three months before judging results. The studies showing improvement measured outcomes at 12 weeks at the earliest, with continued gains through five to six months.
You’re more likely to notice improvements in how the scar feels (softer, less tight, less itchy) before you see changes in how it looks. Color and thickness changes take longer. For older, fully matured scars that have been stable for a year or more, allantoin alone is unlikely to produce dramatic visible changes, though it can still improve skin texture and hydration over the scar site.
Flat Scars vs. Raised Scars
The type of scar matters. Allantoin’s keratolytic and cell-turnover properties are most relevant to hypertrophic scars, which are raised, firm, and stay within the boundaries of the original wound. These scars have excess collagen that can potentially be softened over time. For flat scars that are mainly discolored, allantoin’s moisturizing properties may help the skin look healthier, but it doesn’t have strong evidence as a pigment-correcting ingredient. A small 2020 study of 31 women found that a regimen containing allantoin and ceramides improved acne symptoms and skin barrier function, but this was about active breakouts and skin health rather than established acne scars.
Keloid scars, which grow beyond the original wound borders and can be quite thick, are the hardest to treat topically. The overnight patch study did include keloids and showed thickness improvements, but keloids often require additional interventions like pressure therapy or injections for meaningful reduction.
Choosing an Allantoin Product
Look for a product that lists allantoin in the active ingredients at 0.5 to 2 percent. Many scar gels combine it with onion extract and heparin, which is the formulation used in most of the clinical research. Products that pair allantoin with silicone give you the benefits of both ingredients, though they tend to cost more.
The vehicle matters too. Gels absorb quickly and work well under clothing. Overnight patches maintain contact with the scar for hours, which may improve ingredient delivery. The patch-based study showing ultrasound-confirmed thickness reduction used extended overnight contact, suggesting that longer exposure time could be beneficial. Whichever format you choose, consistency over weeks and months matters more than any single application.