However, along with its derivatives Sudan III and Sudan IV, the compound has been banned in many countries (including the United States and the European Union)[3][4][5] due to its classification as a category 3 carcinogenic hazard by the International Agency for Research on Cancer (not classifiable due to its carcinogenicity to humans).

The Sudan dyes are a group of azo compounds which have been used to color hydrocarbon solvents, oils, fats, waxes, shoes, and floor polishes.

[9] The bilogical breakdown of the nitrogen-nitrogen bond by hydrogenation of the Sudan I molecule (azo-reduction) produces aniline and 1-amino-2-naphthol.

[citation needed] The C-hydroxylated metabolites may be considered as the detoxification products, while the benzene diazonium ion (BDI), formed by the microsome-catalyzed enzymatic splitting of the azo group of Sudan I, reacts with DNA in vitro.

[12] Moreover, Sudan I strongly induces CYP1A1 in rats and human cells in culture due to the activation of the cytosolic aryl hydrocarbon receptor.

[b] It has been suggested that a CYP- or peroxidase-mediated activation of Sudan I or a combination of both mechanisms may be responsible for the organ specificity of this carcinogen for the liver and urinary bladder in animals.

Exposure to the skin can happen by textile workers being subjected to direct exposure, or by wearing tight-fitting textiles dyed with Sudan I. Allergic reactions are induced when the azo dye binds to the human serum albumin (HSA), forming a dye-HSA conjugate which immunoglobulin E binds to, leading to an eventual release of histamine.

[27] The regulation of Sudan I in Europe started in 2003, after repeated notifications were published in the EU rapid alert system.

The EU rapid alert system announced that Sudan I was found in chili powder and other foods that were prepared with it.

[28] The German Federal Institute for Risk Assessment was asked its opinion and came to the conclusion that Sudan dyes are harmful to health.

[29] This includes that said dyes are forbidden to be used in textiles and leather, that may come in direct and prolonged contact with the skin or oral cavity.

No textiles made of leather material are allowed to be coloured with azo dyes, a specific list of which items can be found in the Official Journal of the European Union.

[30] Furthermore, it is prohibited, in the European Union, to place any textile or leather articles coloured with azo dyes on the market.

To ensure this, they should be members of the ETAD (Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers) from which they can receive their certificate.

[12] Contradictory to the findings in the gastrointestinal tract and liver, there was an increase in micro-nucleated cells found in the bone marrow.

[12] Guanosine DNA adducts derived from peroxidase metabolites of Sudan I were also found in vivo, in the bladder of rats.