Allium cepa, trademarked by Mederma as Cepalin (not to be confused with cephalin) is the active content of mederma derived from an onion called Allium cepa Linn, a readily available and highly researched bioflavonoid with antihistamine and antiproliferative effects on both normal and malignant cells. This product is labeled as made in Germany, or originally developed in Germany.
Water (purified), PEG-4, Aloe Barbadensis Leaf Juice, Allium Cepa (Onion) Bulb Extract, Xanthan Gum, Allantoin, Methylparaben, Sorbic Acid, Fragrance
Mederma is an onion-extract-based topical gel produced by Merz Pharmaceuticals of Greensboro, North Carolina. Mederma's marketing claims it can make scars "softer, smoother, and less noticeable".
Most peer reviewed research articles dispute this however.
One published peer reviewed research article indicated no statistically significant change in hypertrophic scar appearance from products of this type.
Though Mederma appears to do better than nothing at all, it does no better than cheap emollients which simply keep the skin moist.
However, a 1996 study into the therapeutic values of onion and garlic found that they may act as an anti-inflammatory and bacteriostatic and in 2002, researchers found that Mederma improved collagen organization after injury in rabbits.