Ingredient review
Acid Red 33
INCI: CI 45220
A widely used synthetic red dye that adds vibrant color to makeup, but may cause allergic reactions in sensitive individuals.
In plain English
CI 45220, also known as Acid Red 33 or D&C Red No. 33, is a man-made red dye approved for use in cosmetics. It gives products like lipstick, blush, and nail polish their bright red or pink hues. While generally safe for most people, it can occasionally cause skin irritation or allergic reactions, especially in those with sensitive skin or known dye allergies.
Quick decision guide
Useful, but context matters
Acid Red 33 is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Acid Red 33.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
CI 45220 is a synthetic azo dye, meaning it is a colorant created through chemical processes. It is listed as D&C Red No. 33 in the U.S. and is approved for use in cosmetics by regulators like the FDA.
How it works
In a cosmetic product, CI 45220 works by absorbing and reflecting specific wavelengths of light, which creates a visible red or pink color. It is mixed into the product base (like a lipstick wax or nail polish solvent) to evenly distribute the color.
Pros
Vibrant color payoff
Provides a bright, consistent red or pink hue that stays true in various lighting conditions, making it a favorite for lipsticks and blushes.
Regulatory approval
Approved by the U.S. FDA and other global agencies for use in cosmetics, giving consumers confidence in its safety when used as intended.
Cons and cautions
Allergic reaction risk
Can cause contact dermatitis or skin irritation in people sensitive to synthetic dyes, leading to redness, itching, or swelling.
Not natural
As a synthetic chemical, it may be avoided by those seeking natural or organic beauty products, and some consumers prefer plant-based alternatives.
Best for
- People who enjoy colorful makeup and have no known dye allergies
- Those looking for a cost-effective, stable colorant in their cosmetics
Use caution if
- Individuals with a known allergy to azo dyes or red colorants
- People with very sensitive or reactive skin who prefer fragrance-free or dye-free products
Usage tips
Safety summary
CI 45220 is considered safe for most people when used in cosmetics at approved concentrations. However, it can cause allergic reactions in sensitive individuals, so patch testing is recommended for those with a history of dye allergies.
Research notes
Studies confirm that CI 45220 is a low-irritant colorant with a low risk of sensitization in the general population. Allergic reactions are rare but documented, primarily in individuals with pre-existing sensitivities to azo dyes.
Common label clues
- Typical concentration
- Typically used at very low concentrations, often less than 1%
- Regulatory status
- Approved for use in cosmetics by the U.S. FDA (as D&C Red No. 33) and by the European Union (as CI 45220) with concentration limits in some product categories.
- Common uses
- Lipsticks, Blushes, Nail polishes, Eye shadows, Facial makeup
- Environmental note
- As a synthetic dye, it is not biodegradable and may accumulate in water systems if not properly filtered during manufacturing. Some brands are moving toward natural alternatives for sustainability.
Good to know
- CI 45220 is often listed as D&C Red No. 33 in the U.S. and may appear under different names in other countries.
- It is not the same as Red 40 (a food dye), though both are synthetic azo dyes.
Common questions
What is Acid Red 33 in beauty products?
CI 45220, also known as Acid Red 33 or D&C Red No. 33, is a man-made red dye approved for use in cosmetics. It gives products like lipstick, blush, and nail polish their bright red or pink hues. While generally safe for most people, it can occasionally cause skin irritation or allergic reactions, especially in those with sensitive skin or known dye allergies.
What does Acid Red 33 do in a beauty product?
In a cosmetic product, CI 45220 works by absorbing and reflecting specific wavelengths of light, which creates a visible red or pink color. It is mixed into the product base (like a lipstick wax or nail polish solvent) to evenly distribute the color.
Is Acid Red 33 safe for most people?
CI 45220 is considered safe for most people when used in cosmetics at approved concentrations. However, it can cause allergic reactions in sensitive individuals, so patch testing is recommended for those with a history of dye allergies.
Who should be careful with Acid Red 33?
Individuals with a known allergy to azo dyes or red colorants People with very sensitive or reactive skin who prefer fragrance-free or dye-free products
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.