Mederma Advanced Scar Gel is not a silicone gel. Its active ingredient is allantoin, a skin protectant, and its signature ingredient is onion bulb extract. The full ingredient list contains no dimethicone, siloxanes, or any other form of silicone. However, some other products in the Mederma lineup do contain dimethicone (a common silicone), which is where the confusion likely starts.
What Mederma Advanced Scar Gel Actually Contains
The FDA’s drug label for Mederma Advanced Scar Gel lists allantoin as its only active ingredient. The inactive ingredients are water, polyethylene glycol 200, alcohol, xanthan gum, onion bulb extract, panthenol, fragrance, lecithin, methylparaben, sorbic acid, and sodium hyaluronate. None of these are silicone-based compounds.
The formula is built around two key ingredients. Allantoin works as a skin protectant that softens and moisturizes tissue. Onion bulb extract, sometimes marketed under the proprietary name Cepalin, targets the inflammatory process involved in scarring. It contains bioflavonoids that reduce inflammation and slow excess collagen production by skin cells called fibroblasts. The idea is that by calming down the body’s overactive healing response, the scar flattens and softens over time.
Which Mederma Products Do Contain Silicone
The Mederma brand sells several different scar products, and some of them do include dimethicone, which is a silicone. Mederma PM Intensive Overnight Scar Cream lists both allantoin and dimethicone as active ingredients. Mederma Scar Gel for Kids also contains dimethicone. So if you specifically want a Mederma product with silicone, those versions have it. The classic Advanced Scar Gel does not.
This mix of formulas within a single brand makes it easy to assume all Mederma products work the same way. They don’t. Reading the active ingredient panel on the specific product you’re buying is the simplest way to check.
Why the Silicone Distinction Matters
Silicone products, whether sheets or gels, are considered the first-line treatment for raised scars and keloids across dermatology guidelines. They work through an occlusive mechanism: silicone creates a barrier over the scar that traps moisture, hydrates the outer layer of skin, and signals the tissue underneath to slow collagen overproduction. This approach has decades of clinical data behind it and is widely regarded as the gold standard for non-invasive scar management.
Onion extract works through a different pathway entirely, targeting inflammation and mast cell activity rather than forming a physical barrier. The evidence for onion extract alone is more mixed. Some trials have found that simple petroleum-based moisturizers performed as well as or better than onion extract for scar improvement, likely because hydration itself plays a major role in how scars mature.
How They Compare in Practice
A randomized trial published in the Journal of Cosmetic Dermatology compared a silicone gel containing onion extract and aloe vera against traditional silicone gel sheets in 40 surgical patients over 12 weeks. Both groups saw similar results: no significant difference in scarring rates, scar appearance scores, redness, or pigmentation. Pain and itchiness decreased in both groups, and neither caused adverse effects. The silicone-plus-onion-extract gel did show slightly better pliability scores on objective measurement.
This study is worth noting because it tested a combination product, not onion extract on its own. The silicone base in that gel likely contributed to the positive results. It doesn’t tell us much about how a non-silicone onion extract gel like Mederma Advanced would perform head-to-head against a pure silicone gel.
Choosing the Right Scar Product
If you’re looking for a silicone scar gel specifically, Mederma Advanced Scar Gel is not what you want. You’d need to look at Mederma’s overnight cream or kids’ formula, or at dedicated silicone scar gels from other brands like ScarAway, Kelo-cote, or Dermatix. These are pure silicone-based formulas designed to create that occlusive barrier over the scar.
If you already have a tube of Mederma Advanced and you’re wondering whether it works, it can still help with moisturizing and softening scars. The onion extract and allantoin combination has anti-inflammatory properties that some people find beneficial, particularly for newer scars that are still red or slightly raised. Just know that its mechanism is fundamentally different from what a silicone gel does, and the clinical evidence supporting silicone for scar prevention and treatment is stronger overall.
For the best results on a newer surgical or injury scar, many dermatologists recommend starting a silicone-based product early, often within a few weeks of the wound closing. Consistency matters more than brand: applying the product daily for at least 8 to 12 weeks gives it the best chance of making a visible difference.