Science
Mechanism of Action
This synthetic azo dye absorbs light at approximately 530 nm to provide its characteristic color. It acts solely on the surface, significantly not penetrating the stratum corneum, and has no biochemical effect on skin.
Research
Clinical Evidence
High confidenceN/A
Key findings
- 01 At 0.5%, no measurable permeation occurred, indicating negligible systemic exposure with a minimal flux of 5.9–6.6 µg/cm².
- 02 A 25% concentration elicited 0% positive reactions, demonstrating no skin sensitizing potential.
- 03 1.0% formulation showed no skin irritation or systemic toxicity after 65 applications.
Transparency
Dusting Analysis
The Formula
Formulation
Stability
Stable under normal conditions, but color may shift to brown or orange at extreme pH levels. Requires UV filters in transparent packaging to prevent light-induced fading.
Conflicts
- Strong oxidizing agents
- Strong reducing agents
- Uncoated alumina/silica (can cause precipitation if not formulated as a lake)
Safety
Safety Profile
CIR defers to FDA, which permits up to 3% in external cosmetics, including lipsticks. EU SCCS limits to 0.5% in non-oxidative hair dyes and strictly prohibits its use in the eye area (FDA/EU).
Your Skin
Skin Compatibility
Our Assessment
Verdict
Acid Red 33 is a valuable colorant, offering a vibrant purple-red hue with a robust safety profile and broad compatibility across all skin types.
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References
Sources