D&C Brown No. 1 is an orange azo dye, known as ACID ORANGE 24, CI 20170

Chemical name: sodium;4-[(2Z)-2-[(5E)-5-[(2,4-dimethylphenyl)hydrazinylidene]-4,6-dioxocyclohex-2-en-1-ylidene]hydrazinyl]benzenesulfonate

What it is used for and where

Cosmetics

It is a restricted ingredient as II/1232 a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009.

Colorant to avoid. It is an ingredient that makes the final product more attractive from an aesthetic point of view, but can pose a potential health risk with undesirable side effects especially when used continuously as it can be absorbed through the skin or mucous membranes. 

Safety

 The problem with azo dyes (monoazo or diazo) is photocatalytic degradation leading to oxidation and the subsequent formation of impurities such as aromatic amines, some of which have carcinogenic activity.

Chemical safety

• Molecular Formula   C₂₀H₁₇N₄NaO₅S
• Molecular Weight      448.4 g/mol
• CAS      1320-07-6    6371-84-2 
• UNII    8796B4I6HE
• EC Number       215-296-9
• DTXSID7041708

Synonyms: 

sodium;4-[(2Z)-2-[(5E)-5-[(2,4-dimethylphenyl)hydrazinylidene]-4,6-dioxocyclohex-2-en-1-ylidene]hydrazinyl]benzenesulfonate

Benzenesulfonic acid, 4-((3-((dimethylphenyl)azo)-2,4-dihydroxyphenyl)azo)-, monosodium salt