Laser treatment has become common practice for beauticians and dermatologists who use laser pulses to introduce heat into the skin, which promotes skin cells to produce more collagen – the protein that gives skin its firmness and elasticity. While the effects of light has been studied for quite some time, Eindhoven University of Technology (TU/e) researcher, Susanne Dams says there is still little understanding of the effect of the heat introduced by a laser light. Research performed by Dams, which she describes in her dissertation for which she gained her PhD from TU/e’s Biomedical Engineering Department, now provides a better understanding of this process. She first tested the effect of heat on cell cultures, by giving them heat shocks of 45 and 60 °C without a laser. This excluded possible effects generated by the laser light. Subsequently, she conducted similar tests on pieces of excised human skin, and at a later stage she heated pieces of skin with a laser. The results of these tests were in line with the earlier tests. She showed that the heat shocks led to increased production of collagen, which is considered to be one of the important factors in skin rejuvenation. The production of this protein by the human body declines after the age of 25, causing wrinkles to form and making the skin sag. The best effect was found to result from a heat shock of 45 °C lasting eight to ten seconds. It was also shown that higher temperatures cause damage to the skin cells. Dams established in her tests that heating cells in culture for two seconds at 60 °C results in cell necrosis. The question of how long the skin-rejuvenating effect of the laser treatment lasts remains unanswered for the moment. Dams discovered that after a heat shock the gene expression (the precursor to the formation of the protein) returns to its normal level after 48 hours. However, the extra collagen produced as a result of the increased gene expression contributes to skin rejuvenation for a longer period. Although this study suggests that it is heat rather than light that rejuvenates the skin, the laser still remains the instrument of choice in the opinion of Dams. "A laser allows treatment with great precision, because it can specifically heat specific elements in the skin while leaving the rest unharmed. This allows the optimal effect to be achieved," Dams said. Dams conducted her research in cooperation with Philips Research Eindhoven. For more information, visit: www.tue.nl