Mederma is a topical product used to improve scar appearance. It is a gel based on an onion extract and produced by Merz Pharmaceuticals of Frankfurt, Germany. Mederma's marketing claims it can make scars "softer, smoother, and less noticeable". Generic versions are sold under the name cepalin.
One 2006 clinical trial found no statistically significant change in hypertrophic scar appearance from products of this type compared to the standard petrolatum emollient, while a 1999 pilot trial found an onion extract gel less effective than the petrolatum.
In contrast, a 54-person trial in 2010, funded by Merz, found that an onion extract cream improved the appearance of stretch marks.
Basic research and animal testing suggest the gel could be effective. 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.
Allium cepa, the common onion, is the active content of Mederma. Onions contain a readily available and highly researched bioflavonoid with antihistamine and antiproliferative effects on both normal and malignant cells.
Merz Pharmaceuticals also produces Contractubex for scars, which also contains onion extract in addition to other ingredients. Contractubex has been found effective in clinical trials for the prevention of hypertrophic scars and keloids in Chinese patients having laser tattoo removal.
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- Chung VQ, Kelley L, Marra D, Jiang SB (February 2006). "Onion extract gel versus petrolatum emollient on new surgical scars: prospective double-blinded study". Dermatol Surg. 32 (2): 193–7. doi:10.1111/j.1524-4725.2006.32045.x. PMID 16442038.
- Jackson BA, Shelton AJ (April 1999). "Pilot study evaluating topical onion extract as treatment for postsurgical scars". Dermatol Surg. 25 (4): 267–9. doi:10.1046/j.1524-4725.1999.08240.x. PMID 10417579.
- WebMD. Onion Cream Treats New Stretch Marks.
- K. Augusti, Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.), Indian J Exp Biol 34 (1996), pp. 634–640.
- Saulis, Alexandrina S. M.D.; Mogford, Jon H.; Mustoe, Thomas A. M.D. (2002). "Effect of Mederma on Hypertrophic Scarring in the Rabbit Ear Model". Plastic and Reconstructive Surgery. 110 (1): 177–183. doi:10.1097/00006534-200207000-00029. PMID 12087249.
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- Mederma Gel patient advice, including possible side effects
- Ho WS, Ying SY, Chan PC, Chan HH (July 2006). "Use of onion extract, heparin, allantoin gel in prevention of scarring in chinese patients having laser removal of tattoos: a prospective randomized controlled trial eczema". Dermatol Surg. 32 (7): 891–6. doi:10.1111/j.1524-4725.2006.32192.x. PMID 16875470.