Castellani’s paint or magenta paint has been used to treat fungal skin infections since the 1920s. Magenta has also been used in hair dyes, cosmetic products and artist paints. Several studies have shown that people who work in dye-making factories that produce magenta have a higher risk of bladder cancer than the general population. The International Agency for Research into Cancer (IARC) classifies different things according to their cancer risk – they have listed the production of magenta as high risk, meaning there is conclusive evidence that working in such as job could cause cancer, likely because of exposure in the production process to a chemical called ortho-toluidine. However, evaluations by IARC have found no evidence of magenta as a product increasing cancer risk. There is also no clear evidence that other ingredients in Castellani’s paint, aside from the dyes that make up magenta, pose any risk of cancer.