Re: Can putting ultra violet light in a room reduce view of veins in drug abuse

I have heard of no effect whereby veins become visible when 
illuminated by UV light. Human eyes are not sensitive to UV photons, 
so under pure UV light nothing would be visible unless there 
were some fluorescence effect of which I am not aware. Furthermore, 
UV radiation can be very dangerous, and can be used only when 
emitted by properly designed and installed lamps for specific 
applications, such as germicidal purposes. So, I do not recommend 
UV for the use you have in mind. What you might try is a blue light. 
Veins under the skin tend to appear blue because the skin above 
tends to absorb some of the red light which the venous blood 
reflects, leaving the bluish remainder to be seen. If only blue light 
were used to illuminate the skin, then everything would reflect the 
same blue color, and the veins might not be so readily visible. In 
contrast, a red light might make the veins stand out more. You can try 
this on yourself with a regular incandescent lamp and red and blue 
filters, or with a blue incandescent bulb and a red one.