Ingredient review

Acid Red 18

INCI: CI 24790

A widely used synthetic red dye that is generally safe in cosmetics at low levels, but may cause allergic reactions in sensitive individuals.

beautyskincarecolorant

In plain English

CI 24790 is a man-made red colorant, also known as Acid Red 18 or Ponceau 4R. It is added to cosmetics like lipstick and blush to give them a bright red or pink shade. It is not a skin-care active ingredient—it only changes the product's appearance. While most people can use it without issues, a small number may experience skin irritation or allergic reactions.

Quick decision guide

Read the cautions before using

Acid Red 18 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 18.
  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 24790 is a synthetic azo dye, meaning it contains a nitrogen-based chemical structure that produces a red color. It is approved for use in cosmetics in many countries, including the U.S. and EU, under strict concentration limits.

How it works

It works by absorbing and reflecting specific wavelengths of light, making the product appear red or pink. It does not interact with the skin's biology; it simply sits on the surface as a colorant.

Pros

Vibrant color payoff

Delivers a bright, consistent red shade that stays true in the formula.

Good stability

Resists fading from light and heat, so your product keeps its color over time.

Cons and cautions

Allergy risk

A small percentage of people may develop contact dermatitis or hives from azo dyes like this one.

Not natural

Synthesized from petroleum-derived chemicals, which may be a concern for those preferring natural ingredients.

Best for

  • Anyone looking for a bold red or pink color in their makeup
  • People without known sensitivity to synthetic dyes

Use caution if

  • Individuals with known allergies to azo dyes or Ponceau 4R
  • Those seeking exclusively natural or plant-based colorants

Usage tips

Patch test a new product containing CI 24790 on your inner arm before using it on your face or lips.
If you have sensitive skin or a history of dye allergies, choose products with iron oxides or carmine instead.

Safety summary

Generally recognized as safe in cosmetics at low concentrations. The main risk is allergic contact dermatitis in sensitive individuals. Regulatory bodies set strict purity and usage limits.

Research notes

Studies show low acute toxicity and no evidence of carcinogenicity in cosmetic use. Allergic reactions are rare but documented. The Cosmetic Ingredient Review (CIR) panel has deemed it safe as used.

Common label clues

Typical concentration
Typically less than 1% in rinse-off products; up to a few percent in leave-on color cosmetics
Regulatory status
Approved for use in cosmetics in the U.S. (FDA) and EU (EC) with concentration limits. Banned in some countries for food use but still allowed in cosmetics.
Common uses
Lipsticks, Blushes, Eye shadows, Nail polishes, Bath products
Environmental note
Synthetic azo dyes can persist in wastewater and may have environmental impacts if not properly treated. Some brands are moving toward natural alternatives.

Good to know

  • CI 24790 is also used as a food dye (Ponceau 4R) in some countries, but cosmetic-grade versions are tested for purity.
  • In the EU, it is listed as a permitted colorant with specific purity requirements.

Common questions

What is Acid Red 18 in beauty products?

CI 24790 is a man-made red colorant, also known as Acid Red 18 or Ponceau 4R. It is added to cosmetics like lipstick and blush to give them a bright red or pink shade. It is not a skin-care active ingredient—it only changes the product's appearance. While most people can use it without issues, a small number may experience skin irritation or allergic reactions.

What does Acid Red 18 do in a beauty product?

It works by absorbing and reflecting specific wavelengths of light, making the product appear red or pink. It does not interact with the skin's biology; it simply sits on the surface as a colorant.

Is Acid Red 18 safe for most people?

Generally recognized as safe in cosmetics at low concentrations. The main risk is allergic contact dermatitis in sensitive individuals. Regulatory bodies set strict purity and usage limits.

Who should be careful with Acid Red 18?

Individuals with known allergies to azo dyes or Ponceau 4R Those seeking exclusively natural or plant-based colorants

Research sources

Cosmetic Ingredient Review (CIR) - Safety Assessment of CI 24790OpenFDA - Color Additives Permitted for Use in CosmeticsOpenPubMed - Allergic contact dermatitis from Ponceau 4ROpen

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.