Authorities in Britain and Ireland tested fake fragrances they seized and detected urine.
Experts speculate it is used as a pH balance stabilizer and for its color.
Harper's Bazaar Magazine says other studies have found bacteria and anti-freeze.
Dermatologists say fake perfumes can cause contact dermatitis, a reaction that is not normally seen from real perfumes.
"They will invariably say that they felt different as soon as they put it on. They felt burning. They saw redness. It felt uncomfortable, it didn't smell right," says dermatologist Jeannette Graf.
Some of the tell-tale signs of counterfeits: loose cellophane, thin boxes, and barcodes on the side instead of the back.
Experts also say the money spent on counterfeit goods in some cases goes toward supporting child labor, drug cartels, and terrorist groups.
