Database/Hair Dyeing/Acid Red 33
Mostly petroleum · ISO 16128

Is Acid Red 33 natural?

Mostly not. Aromatic azo-dye backbone is petrochemical; two sulfonate salt groups are counted as mineral-origin on an estimated structure.

INCI nameAcid Red 33
CAS3567-66-6
FormulaC16H11N3Na2O7S2 · 467.4 Da
FunctionHair Dyeing
FeedstockSynthesised from petrochemical naphthalenesulfonic acid and aniline-type intermediates…

How we scored it

Estimated naphthalene-disulfonic azo structure, MW~467; 2x SO3Na ~206Da natural (mineral) / ~261Da petrochemical backbone; 206/467=0.44
What counts. ISO 16128-2 scores the atoms that remain in the final ingredient. Reagents, solvents, catalysts and protecting groups used during manufacture leave no mass behind and are not counted.

Where it comes from

Synthesised from petrochemical naphthalenesulfonic acid and aniline-type intermediates via azo coupling. No natural manufacturing route.

In plain English

A synthetic red dye used in hair colourants and cosmetics, made by chemically joining petroleum-derived aromatic building blocks. A small part of its weight is a mineral-type salt group.

CosIng definition: Acid Red 33 is classed chemically as a monoazo colour. It conforms to the formula:

Natural alternatives with the same function

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 Epicatechin 100% natural origin

An antioxidant compound naturally found in tea and cocoa, used in skin, hair and oral care. It's extracted…

 Lawsonia Inermis Extract 100% natural origin

A plant extract from the henna shrub, used to condition hair and skin and add a reddish tint.…

 Pyrogallol 100% natural origin

A hair-dye ingredient traditionally made by heating gallic acid, itself extracted from plant tannins in gallnuts, until it…

Structure

2D structure of Acid Red 33

disodium;5-amino-4-hydroxy-3-phenyldiazenylnaphthalene-2,7-disulfonate

PubChem CID 19116 ↗

References

  1. 1ISO 16128-1:2016 and ISO 16128-2:2017 — Guidelines on technical definitions and criteria for natural and organic cosmetic ingredients and products. ISO, Geneva.
  2. 2Acid Red 33. PubChem CID 19116. National Center for Biotechnology Information. pubchem.ncbi.nlm.nih.gov ↗
  3. 3ACID RED 33. CosIng — European Commission cosmetic ingredient database. ec.europa.eu/cosing ↗
  4. 4ACID RED 33. CosIng u2014 European Commission database for information on cosmetic substances and ingredients. https://ec.europa.eu/growth/tools-databases/cosing/search?search=ACID%20RED%2033