Ingredient review

Acid Red 52

INCI: CI 45100

A widely used synthetic red dye that adds color to cosmetics but offers no skincare benefits.

beautyskincarecolorant

In plain English

CI 45100 is a man-made red dye that gives lipsticks, blushes, and other makeup their pink or red color. It doesn't treat or improve your skin—it's purely for appearance. While generally considered safe in small amounts, some people may experience irritation, especially if they have sensitive skin or allergies to synthetic dyes.

Quick decision guide

Useful, but context matters

Acid Red 52 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.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Acid Red 52.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. 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

low

Less likely to sting, burn, or bother most users, though sensitive skin can still react.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

moderate

There is useful support, but formula details and claim strength still matter.

What it is

CI 45100 is a synthetic organic dye from the xanthene family, specifically a disodium salt of 3',6'-dihydroxy-2',4',5',7'-tetraiodospiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3-one. It is also known as Acid Red 52 and is approved for use in cosmetics in many regions.

How it works

In a cosmetic product, CI 45100 dissolves or disperses in the formula to impart a uniform red or pink color. It works by absorbing certain wavelengths of visible light and reflecting others, creating the color you see. It does not interact with the skin's biology.

Pros

Vibrant color payoff

CI 45100 delivers a bright, consistent red or pink shade that stays true on the skin, making it a favorite in lipsticks and blushes.

Good stability

This dye remains stable across different pH levels and doesn't easily fade, so your makeup color lasts longer.

Cons and cautions

Potential allergen

Some people may develop contact dermatitis or irritation from synthetic dyes like CI 45100, especially on sensitive areas like lips or eyes.

No skin benefit

Unlike active ingredients such as niacinamide or hyaluronic acid, CI 45100 does nothing for your skin's health—it's purely cosmetic.

Best for

  • Anyone looking for colorful makeup products
  • Those without known sensitivities to synthetic dyes

Use caution if

  • Individuals with known allergies or sensitivities to synthetic colorants
  • Those seeking natural or organic cosmetics

Usage tips

Patch test any new colored product on a small area of skin before full use, especially if you have sensitive skin.
Check the full ingredient list if you have known allergies to synthetic dyes.

Safety summary

CI 45100 is generally recognized as safe for use in cosmetics at typical concentrations, but it can cause allergic reactions in sensitive individuals. Regulatory bodies have set limits on its use, especially near the eyes.

Research notes

Studies indicate low acute toxicity and minimal skin penetration, but there is limited long-term data on chronic exposure. Most safety assessments rely on industry data and regulatory reviews.

Common label clues

Typical concentration
0.1% to 1%
Regulatory status
Approved for use in cosmetics in the U.S. (FDA) and EU (Annex IV), but restrictions may apply for eye-area products in certain regions.
Common uses
Lipsticks, Blushes, Eyeshadows, Nail polishes, Hair dyes
Environmental note
As a synthetic dye, CI 45100 is not biodegradable and may contribute to water pollution if not properly filtered during manufacturing.

Good to know

  • CI 45100 is approved by the U.S. FDA for use in cosmetics, but it is not allowed in products intended for use around the eyes in some countries.
  • It is sometimes listed as 'Acid Red 52' on ingredient labels.

Common questions

What is Acid Red 52 in beauty products?

CI 45100 is a man-made red dye that gives lipsticks, blushes, and other makeup their pink or red color. It doesn't treat or improve your skin—it's purely for appearance. While generally considered safe in small amounts, some people may experience irritation, especially if they have sensitive skin or allergies to synthetic dyes.

What does Acid Red 52 do in a beauty product?

In a cosmetic product, CI 45100 dissolves or disperses in the formula to impart a uniform red or pink color. It works by absorbing certain wavelengths of visible light and reflecting others, creating the color you see. It does not interact with the skin's biology.

Is Acid Red 52 safe for most people?

CI 45100 is generally recognized as safe for use in cosmetics at typical concentrations, but it can cause allergic reactions in sensitive individuals. Regulatory bodies have set limits on its use, especially near the eyes.

Who should be careful with Acid Red 52?

Individuals with known allergies or sensitivities to synthetic colorants Those seeking natural or organic cosmetics

Research sources

FDA Color Additive Status ListOpenCosIng Database - CI 45100OpenPubMed - Safety of xanthene dyesOpen

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.