It’s night time, you are in a club, the music plays loud, you enter the toilet in need. Suddenly you are dazzled with bright, fluorescent blue light that makes your visit to this place a rather unpleasant experience. The blue, almost ultraviolet colour not only makes your teeth, eyes and nails shine unnaturally, but it also makes it hard to see the veins or white powders lying on bright surfaces. It is a way to fight drug addiction that gains increasing popularity in Europe and around the world. Public toilets at petrol stations, night shops or train stations radiate now a blue shimmer. However, controversies around the use of such light are increasing, as some specialists involved in drug prevention argue that the difficulties in recognizing veins contribute to non-venous injections, which are very life-threatening.