Re: What other chemical can cause a false positive in a black light urine test?

The "black light" is a light which illuminates the area with ultraviolet 
radiation or uv light.  Substances that appear in this light exhibit 
fluorescence and are emitting light at a higher wavelength and appear to 
"glow" in the dark.  Urine is one substance that can be detected by a uv 
light but there are many other substances that can fluoresce including 
saliva, semen, perspiration, household cleaners, etc.  The uv light aids 
in locating a stain but further testing must then be performed upon the 
stained area to confirm the identity of the substance.

Dale L. Laux