Silicone gel (sheeting)

Topical silicone gel sheeting has been a well-established management of scars since its introduction in the early 1980s, and its therapeutic effects on predominantly hypertrophic scars have been well documented in the literature31–35. Current opinion suggests that occlusion and normalisation of transepidermal water loss (TEWL) are likely the underlying mechanisms of the therapeutic action of silicone gel (sheeting) rather than an inherent anti-scarring property of silicone itself36, 37. Silicone sheets should be applied for 12 or more hours per day for at least 2 months, beginning 2 weeks after wound healing. More studies are supporting the use of silicone gels, particularly in areas of consistent movement where sheeting will not conform38–42. Based on current data, silicone gels may be comparable to silicone gel sheets with regard to their efficacy41, 43 and can be recommended for excessive scar-prone patients or in specific anatomic locations, and should be applied twice daily beginning approximately 2 weeks after surgery or initial trauma. Recently, the combination of a silicone gel and a sun protection agent has been manufactured (Kelocote UV, Sinclair IS Pharma, London, UK).

Onion extract

It is currently believed that the flavonoids (quercetin and kaempferol) in onion extract play a significant role in reducing scar formation through the inhibition of fibroblast proliferation and collagen production. A study by Phan et al suggested that these inhibitory effects may be mediated through inhibition of transforming growth factor beta (TGF-β1, -2) and SMAD proteins by quercetin44, 45. An increasing number of studies testing the ultimate benefit of onion extract containing scar creams are available46–48. A scar cream containing the active substances extractum cepae, allantoin and heparin appears to be effective in improving scar appearance49–52 and preventing scarring in patients having laser tattoo removal53. Its use has also proven successful in combination with intralesional triamcinolone acetonide54 or ultrasound55, 56 for the therapy of keloid and hypertrophic scars or mature scars, respectively. Based on the recently published German Guidelines for the treatment of pathological scarring, combination preparations containing onion extract can be considered for postoperative prophylaxis of de novo development of hypertrophic scars or keloids, as well as for the prevention of recurrence after surgical therapy of excessive scarring23.

Imiquimod 5% cream

Imiquimod 5% cream, a topical immune response modifier, has been approved for the treatment of genital warts, superficial basal cell carcinoma, and actinic keratoses57. Imiquimod stimulates interferon, a proinflammatory cytokine, which increases collagen breakdown. Additionally, imiquimod alters the expression of apoptosis-associated genes58. It has been used in a variety of trials and observational studies to reduce keloid recurrence after excision and was reported to have positive effects on the recurrence rate of keloids if applied post-surgery59–62.

However, in a recent prospective, double-blind, placebo-controlled pilot study of 20 patients undergoing keloid excision and subsequent treatment with imiquimod 5% cream or placebo, no significant differences in 6-month keloid recurrence rates were detected between groups owing to lack of statistical power63. Another study revealed contradicting data (keloid recurrence in eight out of 10 patients treated with imiquimod 5%)64. Therefore, additional studies may be necessary to further characterise its side-effect profile (persisting inflammation, erosion, depigmentation, etc.) and the ultimate success rates of this rather expensive approach for the reduction of recurrence rates after keloid surgery.