Fighting scar wars? Let the silicone be with you
Gel sheets work, but no one knows why
By Liza G. Ovington, PhD
Program Director, Wounds and Continence
Columbia Healthcare Corp., Fort Lauderdale, FL.
Silicone gel sheeting is a material that has evolved not for the treatment of open draining wounds but for the sometimes extreme results of wound healing in certain patients: hypertrophic or keloid scars. Since the early 1980s, researchers and clinicians have been investigating the beneficial effect of silicone gel sheets on scars. These benefits are manifested as any or all of the following changes in the scar:
• a color change (toward that of surrounding skin);
• a texture change (softening of the scar, increased pliability);
• a change in size (scar tissue mass decreases).
The earliest studies were performed in burn patients but subsequent studies have documented similar beneficial effects on scar formation after surgery, trauma, or various chronic diseases. The therapy appears to work on patients with fresh scars as well as those with scars of long duration (up to 12 years).
In general, the patient applies the silicone gel sheet directly to the scar, without pressure, and leaves it in place for eight to 12 hours per day for several months. The silicone gel sheets look similar to clear gelatin. Most of them are naturally sticky and will stay in place on skin fairly well. However, different types of tape can be used to anchor them if desired. Because the gel sheet is placed onto intact, albeit scarred skin, there are no absorbent demands placed on the silicone. In fact, silicone gel sheets are nonabsorbent. When used for scar therapy, the gel sheets may be washed gently by hand with mild soap and water and reapplied multiple times. Over time, the silicone gel may break up, especially if placed in a high friction area or picked at.
Why gel sheeting works remains a mystery
The mechanisms by which the silicone gel sheeting achieves its positive effects on scarring are not yet well understood. Originally, the sheets were used beneath pressure garments in burn scar therapy, and it was thought that pressure alone accounted for the positive effects, with the silicone gel just serving to evenly distribute the pressure. This was subsequently shown not to be true when the silicone gel sheets alone without external pressure application achieved the same effects on scars.
Later it was postulated that the silicone gel sheets were releasing silicone into the scar tissue, and somehow that generated the effect. Research studies showed that this, too, was not the case. It has been well documented that there are no silicone monomers or extracts available from the gel sheeting form of the product (unlike liquid silicone in breast implants).
Then it was thought that the silicone sheet was simply providing occlusion of the scar tissue and that the subsequent hydration of the tissue was responsible for the change in the scar. Research comparing scar occlusion by a silicone gel sheet vs. occlusion by a hydrocolloid dressing or hydration via a moisturizer documented that only the silicone gel sheet changed the nature of the scar.1 However, another study compared occlusion of scars by silicone gel sheets vs. occlusion by hydrogel sheets and found similar beneficial effects from both materials.2
To date there is no clear evidence to explain the therapeutic effect of silicone gel on scar tissue. However, many studies have documented the end result. The products have been prospectively shown to minimize scar development as well as achieve changes in scars of long duration. (Examples of commercially available silicone gel sheeting products are shown in the table above.)
References
1. Phillips TJ, et al. A randomized controlled trial of hydrocolloid dressing in the treatment of hypertrophic scars and keloids. Dematol Surg 1986; 22:775-778.
2. Ricketts CH, et al. Cytokine mRNA changes during the treatment of hypertrophic scars with silicone and nonsilicone dressings. Dermatol Surg 1996; 22:955-959.
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