Basic Blue 99
INCI: BASIC BLUE 99
Reviewed by Daisy · Last updated 14 Aug 2026
A direct hair colourant primarily used in temporary and semipermanent hair dyes
Effective Concentrations
0.004-2%
Usage Frequency
As directed on product packaging
What Is Basic Blue 99?
Basic Blue 99 is a synthetic organic colorant belonging to the class of direct, nonoxidative hair dyes. It is derived from coal tar sources and functions as a pigment that deposits colour onto the hair fibre without requiring a chemical developer or oxidation process.
In cosmetic formulations, Basic Blue 99 is used to impart blue tones in temporary and semipermanent hair colour products. It is not typically found in skincare formulations; its primary application is in hair colouring where it works by directly adhering to the hair shaft.
How It Works
As a direct dye, Basic Blue 99 does not undergo oxidation. Instead, it is a charged molecule that directly binds to proteins in the hair structure, particularly keratin, without requiring a developer or hydrogen peroxide. This mechanism makes it suitable for temporary and semipermanent colour applications.
When formulated into hair products, the dye molecules penetrate the outer layers of the hair shaft and remain there until gradually fading with washing and environmental exposure.
Clinical Evidence & References
Safety assessments indicate that Basic Blue 99 is used at concentrations ranging from 0.004% to 2% in hair dye formulations. Regulatory bodies have designated coal tar hair dyes containing this ingredient as exempt from certain adulteration provisions when appropriate warning labels and patch test instructions are provided.
In vitro studies using 3D human epidermis models suggest that Basic Blue 99 induces cell death through apoptosis in skin cells, though genotoxic effects have not been observed in the same models. However, these are laboratory findings and do not necessarily reflect behaviour in real-world use when applied to hair rather than skin. Limited case reports of allergic contact dermatitis exist in occupational settings, particularly among hairdressers with repeated exposure.
How to Use
Basic Blue 99 is designed for application to hair, not skin. If using a hair dye product containing this ingredient, follow the manufacturer's instructions carefully. A patch test is recommended 48 hours before application to identify potential skin sensitivity. Apply the product to hair according to timing guidelines, avoid contact with eyes and scalp skin where possible, and rinse thoroughly after the recommended processing time.
Safety & Precautions
Frequently Asked Questions
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