Updates on Using and Understanding Light in Dermatology

In this presentation, dermatologist Harvey Louis from the University of British Columbia discusses the latest understandings and recommendations regarding the use of light in dermatology. He begins by discussing the three major types of light: ultraviolet (UV), visible, and infrared, noting their properties and effects on the skin. UV light, which has high photon energy, primarily causes chemical reactions without immediate effects, often leading to delayed damage like sunburns. Visible light penetrates the skin and can cause heating and indirect chemical reactions. Infrared light penetrates deeply, primarily causing thermal effects. Louis highlights important misconceptions about sunscreen use, such as the outdated belief that sunscreen must be applied 30 minutes before sun exposure; in reality, modern sunscreens provide immediate protection. He discusses the difference between chemical and physical filters, debunking myths about their function and absorption. Furthermore, he addresses the emerging awareness that visible light can also have negative effects on the skin, such as causing pigmentation, and suggests that formulations incorporating iron oxide may offer protection against this. Louis concludes by acknowledging challenges related to sunscreen use, including misinformation, cost issues, and regulatory uncertainties. He emphasizes that effective photo protection goes beyond just sunscreen application, encouraging practices such as seeking shade and wearing protective clothing. The presentation ends with an invitation for a colleague to discuss further topics on UV light.