When should you use sunscreen? Only when you go to the beach or are out in the sun? Or even when you’re working from home? Or during the winter months? The fact is that you are exposed to various wavelengths of harmful UV rays on a daily basis. While UVB rays are more intense around noon and during the summer months, UVA rays are present throughout the day and year. UVA rays also penetrate glass and hence you are exposed to them even indoors if you’re in a room with windows. Another wrinkle is the steady increase in exposure to blue light. For most of human history, we have used firelight, candlelight or incandescent light after sunset. These are all yellow lights and their wavelengths are generally not harmful. However, in recent years we have increasingly moved towards using white lights. These are used not only after sunset but also during the day in most workspaces. These wavelengths have been shown to cause skin damage and a good broad-spectrum sunscreen is essential.