Cocaine users are reportedly flooding hospitals with blackened, dying skin and compromised immune systems. The culprit is not the cocaine itself, but the white powder being used to cut the drug.
The foreign substance causing all the trouble is levamisole, a veterinary de-worming drug. According to the DEA, three-quarters of cocaine seized by the agency has this animal medicine. Drug traffickers are choosing levamisole because it's inexpensive and produces euphoria and hyperalertness as side effects.
Cocaine users are unknowingly inhaling it and experiencing a very,very bad allergic reaction. In some cases, the skin damage is so extensive that a graft and plastic surgery is needed. [Scientific American]