Studies: Onions Improve Appearance of Scars

onion-silicone gel for scarring

Onions can help the appearance of this scar. Photo by Olly Farrell

Onions might be smelly, they can significantly improve the appearance of scars.

Onions contain a number of medicinal compounds. These include allylsulfides, cycloalliin, quercetins, isorhamnetin, mannose, flavonoids, flavinols, cysteine sulfoxides, selenium, thiosulfinates and sulfur compounds.

These compounds combine to offer onion the unique ability to stimulate the healing processes of the skin.

Onions reduce skin scars

Researchers from Thailand’s Chulalongkorn University have confirmed that onions can significantly reduce skin scars.

The researchers tested a silicone derivative gel with 10% onion extract in 39 children who had received surgery requiring the opening of the sternum – also called median sternotomy.

The patients were divided into two groups and the onion gel or a placebo gel was applied to the scars using a split-scar method. This method splits the scar into halves and applies one part of the scar with one gel and the other part of the scar with the other gel.

The treatment was applied to each patient for six months, starting from seven days after their sternotomy surgery.

A median sternotomy is when the sternum is opened – also called “cracking” the sternum – to enable surgeons to treat congenital heart issues or otherwise operate on the heart. It leaves a scar in the middle of the chest.

Scar healing comparison

The researchers recorded the scar healing with progressive photographs along with the Vancouver Scar Scale. Of the 39 that began the study, 36 completed the six-month treatment.

The onion gel-treated group had six children who’s scarring completely disappeared (20%), while only one child among the placebo group was devoid of scarring.

Among the rest of the groups, only 9 of the onion-gel group was left with hypertrophic scarring while 18 of the placebo group had thick scarring – twice the rate.

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A hypertrophic scar will remain red with definite boundaries where the scar meets the normal skin. The tissue will typically be raised over the skin due to a build up of excess collagen. This contrasts keloid scarring, where the scar will be significantly more raised, with the appearance of a bubble at the scar.

Keloid scarring and possibly hypertrophic may be related to genetics, as it has been observed that darker-skinned individuals have a greater risk of keloid scarring. However, this does not eliminate the role of diet.

The researchers concluded that the onion-gel significantly decreased the incidence of hypertrophic scarring. This was seen across the board among the onion-gel group when the applied to the Vancouver Scar Scale. However, the onion-gel didn’t seem to help reduce keloid scarring among those children with keloid scars.

The researchers concluded:

“Onion extract in silicone derivative gel can significantly decreased the incidence of hypertrophic scar from median sternotomy wound in pediatric patients.”


Not the first study

This is not the first study that has investigated this onion-silicone gel. A 2012 study from Thailand’s Khon Kaen University studied 60 children patients also after median sternotomy.

This study found that after three months of treatment with either the onion-gel or a placebo gel, those receiving the onion gel had less itching, less pain and a greater reduction of red pigmentation around their scars. The researchers concluded:

“A silicone derivative plus onion extract gel is safe and effective for the preventing the hypertrophic scarring after median sternotomy.”

What about silicone for scars?

In terms of the silicone aspect of the gel, other research has shown some benefit to silicone gel. A 2009 study explained how silicone aids wound healing:

“Silicon gel exerts several actions which may explain this benefit in scars:

• It increases hydration of stratum corneum and thereby facilitates regulation of fibroblast production and reduction in collagen production. It results into softer and flatter scar. It allows skin to “breathe”.
• It protects the scarred tissue from bacterial invasion and prevents bacteria-induced excessive collagen production in the scar tissue.
• It modulates the expression of growth factors, fibroblast growth factor β (FGF β) and tumor growth factor β (TGF β). TGF β stimulates fibroblasts to synthesize collagen and fibronectin. FGF β normalizes the collagen synthesis in an abnormal scar and increases the level of collagenases which breaks down the excess collagen. Balance of fibrogenesis and fibrolysis is ultimately restored.
• Silicone gel reduces itching and discomfort associated with scars.”

But silicone gel can also come with some adverse side effects such as skin irritation and it can be uncomfortable as a dressing, especially in hotter temperatures. Side effects of silicone injected into the body are well known – including neuralgia and Raynaud’s syndrome – but few side effects have been seen in skin application for short periods.

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Then there is the onion extract

But it appears from this study that onion extract added to the silicone provides an even better resolution of scarring than the silicone alone. What is it about the onion extract? And can onion extract gel decrease scarring without the silicone?

It certainly can. While some studies have found little difference between onion gel and placebo, these were studies among patients with a low risk of hypertrophy. A 2012 study of 16 women patients who underwent cesarean sections with more risk of hypertrophy showed definite benefit. The women’s scars were treated with either a 12% topical onion gel or a “vehicle-based” placebo gel seven days after surgery on a split-scar method. The gel was applied three times daily.

The onion gel-applied scars had significantly less hypertrophy and lower mean scar heights at weeks four and twelve of the treatment.

Onions (Allium cepa) famously contain the antioxidant immune-stimulating quercetin. It also contains thioallyls also called alliins that break down into sulfides. The combination of cysteine sulphoxides and other antioxidants such as ascorbic acid repel microorganisms and free radicals. But the quercetin in onions appears to be its active ingredient in the case of wound healing.

Indeed, laboratory studies have shown that quercetin decreases fibroblasts, decreases collagen deposits, decreases inflammation and helps stabilize mast cells.

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Wananukul S, Chatpreodprai S, Peongsujarit D, Lertsapcharoen P. A prospective lacebo-controlled study on the efficacy of onion extract in silicone derivative gel for the prevention of hypertrophic scar and keloid in median sternotomy wound in pediatric patients. J Med Assoc Thai. 2013 Nov;96(11):1428-33.

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Jenwitheesuk K, Surakunprapha P, Jenwitheesuk K, Kuptarnond C, Prathanee S, Intanoo W. Role of silicone derivative plus onion extract gel in presternal hypertrophic scar protection: a prospective randomized, double blinded, controlled trial. Int Wound J. 2012 Aug;9(4):397-402. doi: 10.1111/j.1742-481X.2011.00898.x.

Chanprapaph K, Tanrattanakorn S, Wattanakrai P, Wongkitisophon P, Vachiramon V. Effectiveness of onion extract gel on surgical scars in asians. Dermatol Res Pract. 2012;2012:212945. doi: 10.1155/2012/212945.


  • Ph.D. in Natural Health Sciences, Doctorate in Integrative Health Sciences, Board Certified Alternative Medicine Practitioner, California Naturopath. Diplomas in Blood Chemistry, Clinical Nutritional Counseling, Homeopathy, Aromatherapy, Colon Hydrotherapy, certificates in Pain Management and Case Management/Contact Tracing. Has authored more than 30 books and hundreds of periodical articles on natural medicine. Recreational activities include surfing, sailing, running, biking, swimming, SUPing, hiking. Contact: [email protected]

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