Scar gel works by hydrating the outer layer of your skin, which signals the tissue underneath to slow down collagen production and flatten raised, discolored scars. Most scar gels use silicone as their active ingredient, forming a thin, breathable barrier over the scar that mimics the protective function of healthy skin. The result, over weeks to months of consistent use, is a scar that becomes softer, flatter, and less noticeable.
How Scar Gel Works at the Skin Level
When your skin heals from a wound, it produces collagen to close the gap. Sometimes the process overshoots, and you end up with a thick, raised, or discolored scar. Scar gel interrupts this overproduction by keeping the outermost skin layer (the stratum corneum) hydrated. That hydration sends a signal to the collagen-producing cells deeper in the skin, called fibroblasts, telling them to ease up.
Silicone-based gels also influence growth factors that control the balance between collagen buildup and collagen breakdown. One growth factor stimulates fibroblasts to keep producing collagen and structural proteins, while another normalizes that production and increases the enzymes that break down excess collagen. The net effect is that your body restores a balance between building new scar tissue and clearing away the surplus. Over time, this makes a raised scar flatter and more pliable.
What Scar Gel Can Improve
Scar gel is primarily designed for two types of problem scars: hypertrophic scars (raised scars that stay within the boundary of the original wound) and keloids (raised scars that grow beyond the wound’s edges). Both involve excess collagen, which is exactly what silicone gel targets. With consistent use, clinical studies show measurable improvements in four key scar characteristics:
- Height: Raised tissue gradually flattens as excess collagen breaks down.
- Redness (vascularity): The scar’s blood vessel density decreases, fading the red or purple color.
- Pigmentation: Discoloration becomes less pronounced relative to surrounding skin.
- Pliability: Stiff scar tissue softens and moves more like normal skin.
Scar gel works best as a preventive tool, applied to fresh surgical scars or healing wounds to reduce the chance of abnormal scarring in the first place. It can also improve the appearance of existing scars, though older, well-established scars respond more slowly and less dramatically than newer ones.
Silicone Gel vs. Silicone Sheets
Silicone comes in two formats: a topical gel you apply like a lotion, and adhesive sheets you press onto the scar. A meta-analysis of randomized controlled trials found no significant difference in effectiveness between the two. Both produced comparable improvements in scar height, redness, pigmentation, and flexibility.
The practical difference comes down to convenience. Patients in clinical studies found sheets significantly more inconvenient to use than gel, especially on areas that move a lot or are hard to cover (like the face, neck, or joints). Gel dries clear, stays invisible under clothing, and works on irregular surfaces. Sheets can shift, peel, or attract attention. Since both formats perform equally, patient preference and location of the scar are the main factors in choosing one over the other.
Onion Extract and Other Formulas
Not all scar gels rely on silicone. Some popular products, like Contractubex and Mederma, use onion extract (from Allium cepa) as a key ingredient, often combined with allantoin and heparin. A study on post-cesarean scars found that a gel with this combination produced significant reductions in scar redness, pigmentation, and height when used consistently for 24 weeks. The improvements held up both when comparing treated patients to untreated controls and when comparing the treated scar to untreated areas on the same person.
Onion extract works through a different pathway than silicone. It has anti-inflammatory properties and appears to inhibit the overproduction of structural proteins in scar tissue. If silicone-based products irritate your skin, onion extract formulas offer a reasonable alternative with clinical evidence behind them.
When and How to Apply It
Timing matters. Clinical guidelines recommend starting scar gel as soon as the wound is fully closed, which for surgical scars means the day of suture removal or even the day of surgery if the wound is sealed. Starting early gives you the best chance of preventing abnormal scarring before it develops.
Apply a thin layer once or twice daily for three to four months. If the scar still looks red and raised at that point, continuing treatment beyond four months is reasonable. Some clinical protocols recommend up to six months for silicone-based products. Consistency is the key variable: occasional use produces minimal results. The gel needs to stay on the scar for most of the day to maintain the hydration barrier that drives collagen regulation.
Before applying, make sure the skin is clean and fully dry. A thin layer is enough. Silicone gel dries within a few minutes and forms an invisible film, so you can apply sunscreen or makeup over it. Avoid using the gel on open wounds or skin that hasn’t fully closed, as it’s designed for intact scar tissue, not active wounds.
What Scar Gel Won’t Do
Scar gel improves the appearance of scars, but it doesn’t erase them. No topical product can restore scarred skin to its original, pre-injury state. What you can realistically expect is a scar that’s flatter, softer, and closer to your surrounding skin tone. For mild to moderate scarring, that improvement can be substantial enough that the scar is barely visible. For severe keloids or very old scars, gel alone may not be sufficient, and procedures like steroid injections, laser therapy, or surgical revision may be more appropriate.
Scar gel also doesn’t work overnight. Most people notice gradual changes starting around four to six weeks, with continued improvement over several months. If you stop using it after a week or two because nothing seems different, you haven’t given it enough time. Think of it as a slow, steady process rather than a quick fix.