D&C Red No. 34 is a chemical compound, a monoazo synthetic red dye also known by the name  Pigment Red 63, CI 15880 

Chemical Name: calcium;2-[(3-carboxy-2-oxidonaphthalen-1-yl)diazenyl]naphthalene-1-sulfonate

What it is used for and where

Cosmetics

Restricted cosmetic ingredient as  IV/29 (CI 15880) II/1349 (Pigment Red 63:1; CI 15880) a Relevant Item in the Annexes of the European Cosmetics Regulation 1223/2009. Substance or ingredient reported: Calcium 3-hydroxy-4-[(1-sulphonato-2-naphthyl)azo]-2-naphthoate

 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 (1).

Use in hair colouring products is prohibited.

Molecular Formula   C₂₁H₁₂CaN₂O₆S

Molecular Weight     460.5 g/mol

CAS     6417-83-0

EC number 229-142-3

UNII BAN556989E

DTXSID4064347

Synonyms: 

CI 15880 

Pigment Red 63

Deep Maroon

References________________________________________________________________________

(1) Chung KT, Stevens SE Jr, Cerniglia CE. The reduction of azo dyes by the intestinal microflora. Crit Rev Microbiol. 1992;18(3):175-90. doi: 10.3109/10408419209114557.

Abstract. Azo dyes are widely used in the textile, printing, paper manufacturing, pharmaceutical, and food industries and also in research laboratories. When these compounds either inadvertently or by design enter the body through ingestion, they are metabolized to aromatic amines by intestinal microorganisms. Reductive enzymes in the liver can also catalyze the reductive cleavage of the azo linkage to produce aromatic amines. However, evidence indicates that the intestinal microbial azoreductase may be more important than the liver enzymes in azo reduction. In this article, we examine the significance of the capacity of intestinal bacteria to reduce azo dyes and the conditions of azo reduction. Many azo dyes, such as Acid Yellow, Amaranth, Azodisalicylate, Chicago Sky Blue, Congo Red, Direct Black 38, Direct Blue 6, Direct Blue 15, Direct Brown 95, Fast Yellow, Lithol Red, Methyl Orange, Methyl Red, Methyl Yellow, Naphthalene Fast Orange 2G, Neoprontosil, New Coccine, Orange II, Phenylazo-2-naphthol, Ponceau 3R, Ponceau SX, Red 2G, Red 10B, Salicylazosulphapyridine, Sunset Yellow, Tartrazine, and Trypan Blue, are included in this article. A wide variety of anaerobic bacteria isolated from caecal or fecal contents from experimental animals and humans have the ability to cleave the azo linkage(s) to produce aromatic amines. Azoreductase(s) catalyze these reactions and have been found to be oxygen sensitive and to require flavins for optimal activity. The azoreductase activity in a variety of intestinal preparations was affected by various dietary factors such as cellulose, proteins, fibers, antibiotics, or supplementation with live cultures of lactobacilli.