What evidence is there that malachite green, gentian violet and nitrofuran cause cancer?
FDA is aware of two reports issued by the National Toxicology Program on nitrofurans. Nitrofurazone (TR-337 published in June 1988) and Nitrofurantoin (TR-341 published in Sept 1989). Both of these reports concluded that under the conditions of two year feed studies there was clear evidence of carcinogenic activity of these compounds in mice and rats. In 1991, FDA withdrew the approvals of two nitrofuran drugs, nitrofuranzone and furazolidone. These two drugs had several approved new animal drug applications for both poultry and swine. It was determined that these this class of compounds could induce cancer in man or animals. FDA issued a Federal Register Notice in 1991 that explains the reasons for the withdrawal. FDA is also aware of a toxicology study published in June 2004 by the National Toxicology Program on malachite green and leucomalachite green. These compounds were nominated for the study by the FDA due to the potential for consumer exposure, structural similarity to gentian
