CI 26100
Reviewed by Emma · Last updated 14 Aug 2026
Also known as: Ci 26100
An azo dye used primarily for colour in cosmetics, with regulatory scrutiny around safety
Best For Skin Types
All
Usage Frequency
As tolerated
What Is CI 26100?
CI 26100 is a synthetic azo dye — a class of colorant widely used in textiles, cosmetics and industrial applications. In skincare and cosmetics, it serves as a cosmetic colorant, providing pigmentation to formulations. Azo dyes are organic compounds characterised by one or more azo bonds (N=N linkages), which give them their colour properties.
This ingredient appears in a small proportion of skincare products, typically at very low concentrations. Its primary role is aesthetic rather than therapeutic.
How It Works
CI 26100 functions as a colorant through its azo chemical structure, which absorbs and reflects light to produce visible colour. It does not interact with skin biology in a therapeutic way; it remains on or near the skin surface as a pigment.
Clinical Evidence & References
Azo dyes, including CI 26100, have raised regulatory and safety questions due to research highlighting potential concerns. Some azo dyes can break down into aromatic amines — compounds that have been associated with skin sensitisation and allergic reactions in certain populations. The European regulatory framework has subjected azo dyes to scrutiny, and only those deemed safe are permitted in cosmetics sold in the EU.
However, evidence specific to CI 26100's safety profile in cosmetic use at typical concentrations remains limited. Regulatory approval suggests it meets current safety thresholds for cosmetic application, though ongoing monitoring continues. Individual sensitivity varies, and some people report acne-related concerns with products containing azo dyes.
How to Use
If using products containing CI 26100, apply as directed by the specific product formulation. If you have a history of skin sensitivity or reactions to dyes, it may be worth patch-testing first or opting for products with alternative colourants. There is no evidence of benefit from using multiple products containing this ingredient.
Safety & Precautions
Frequently Asked Questions
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