Keloids tend to occur on highly mobile sites with high tension. This study was designed to determine whether body surface areas exposed to large strain during normal activities correlate with areas that show high rates of keloid generation after wounding. Eight adult Japanese volunteers were enrolled to study the skin stretching/contraction rates of nine different body sites. Skin stretching/contraction was measured by marking eight points on each region and measuring the change in location of the marked points after typical movements. The distribution of 1,500 keloids on 483 Japanese patients was mapped. The parietal region and anterior lower leg were associated with the least stretching/contraction, while the suprapubic region had the highest stretching/contraction rate. With regard to keloid distribution, there were 733 on the anterior chest region (48.9%) and 403 on the scapular regions (26.9%). No keloids were reported on the scalp or anterior lower leg. Because these sites are rarely subjected to skin stretching/contraction, it appears that mechanical force is an important trigger that drives keloid generation even in patients who are genetically predisposed to keloids. Thus, mechanotransduction studies are useful for developing clinical approaches that reduce the skin tension around wounds or scars for the prevention and treatment of not only keloids but also hypertrophic scars.

As adhesive tapes were applied repetitively, dermal peeling force gradually increased while the amount of stripped corneocytes decreased. As the cumulative amount of stripped corneocytes increased with repetitive applications, the skin irritation worsened as measured by increased destruction of the skin surface topography and TEWL. These phenomena were more marked with the stronger adhesive tape, and there was seasonal variability.

Background/aims: The dermal peeling force of acrylic adhesive tapes was evaluated in relation to the accumulation of fluid and the number of stripped corneocytes. Methods: Two kinds of tapes that had different water vapor permeability were applied on the flexor side of both forearms in eight healthy male volunteers. The dermal peeling force was measured at 1, 4, 8 and 24 h after application of the tapes. Simultaneously, the electrical conductance of the skin beneath the applied tape and the total area of corneocytes stripped on the adhesive surface of the removed tape, instead of the adhesive area of the tape relative to the skin surface, were measured. Results/Conclusions: The dermal peeling force of the permeable tape gradually increased and that of the occlusive tape decreased. The increase in the former could be caused by the increase in the adhesive area of the tape relative to the skin surface, and the decrease in the latter could be caused by reduction of the bonding force among the corneocytes themselves, according to hydration.

Background/aims: The seasonal variation in various properties of adhesive tapes on the skin was evaluated. Methods: In February, April, and August, five general‐purpose adhesive tapes were applied on the forearms of 12 healthy male volunteers for 24 h. The dermal peeling force, the accumulation of fluid, the amount of stripped corneocytes, and the dermal reaction at 1 h after removal of the tapes were evaluated. Results/Conclusions: The various properties of adhesive tapes on the skin were closely related to the accumulation of fluid beneath the applied tape. Because the accumulation of fluid was significantly higher in summer than in winter, the dermal peeling force was lower in summer than winter. However, the number of stripped corneocytes and the dermal reaction of the inner area under the applied tapes were larger in summer than in winter. Though tha dermal peeling force, the accumulation of fluid, and the number of stripped corneocytes are generally considered as dermal irritation factors, the accumulation of fluid and the number of stripped corneocytes may exert a great influence on the seasonal variation in dermal irritation. On the other hand, the dermal reaction of the edge section had no tendency to vary with season. Because the edge reaction should be caused by interference with skin movement by the stiff backing or the adhesive, it seems to be uninfluenced by the accumulation of fluid.

The relationship between the conformability of adhesive tape, the mechanical property of the adhesive tape not to interfere with skin movement, and irritation of the skin was investigated. In order to assess the conformability of adhesive tape to the skin, a uniaxial method employing film strips connected to a strain gauge was used to measure the elastic property of the skin, with or without application of various elastic tapes. The tension loaded on the strain gauge was measured while the skin was extended by 15% of its original length in a direction across the humeral axis on the flexor side of the upper right arm. The most elastic adhesive tape showed the best conformity to the skin. The same adhesive tapes were applied on the flexor side of both upper arms so that the tape held a piece of sanitary cotton in place for 24 h. Dermal irritation was not so remarkable in the skin under the inner part of the tapes. On the other hand, the skin reaction was much more severe on the skin under the edge portion of the applied tape which showed poor conformability to the skin. These findings seemed to indicate that the skin reaction was caused by localized distortion of the skin under the edge portion of the applied tapes, during movement of the underlying muscle. Actually, the distortion of the skin surface was great in the areas immediately outside the edge of the applied tape. In conclusion, adhesive tape conformable to skin movement reduced localized distortion of the skin during application, resulting in low irritation at the edge of the applied tape.