Ingredient review

CI 50420

INCI: CI 50420

CI 50420 is a synthetic black dye that adds color to cosmetics but may cause irritation in sensitive individuals.

beautyskincarecolorant

In plain English

CI 50420 is a man-made black pigment used to give color to makeup, hair dyes, and other beauty products. It's not a skincare active ingredient—it's purely for appearance. While generally safe in small amounts, it can sometimes irritate sensitive skin or cause allergic reactions.

Review score

Safety, usefulness, and evidence

3.5Good
3.5/ 5

Potentially useful with some tradeoffs

The evidence base is useful, but some claims depend heavily on the formula.

Main practical flags: irritation is moderate; clogging risk is low.

Source
synthetic
Evidence
moderate
Irritation
moderate
Clogging risk
low
How reviews are scored

Quick decision guide

Useful, but context matters

CI 50420 can be useful, but watch for some irritation potential.

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 CI 50420.
  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

moderate

Can bother some users, especially with frequent use, damaged skin, or strong companion ingredients.

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 50420 is a synthetic azo dye that produces a black color. It is listed under the Color Index (CI) system used to identify pigments and dyes in cosmetics and other products.

How it works

In a cosmetic product, CI 50420 works by absorbing and reflecting light to create a black hue. It is mixed into formulations to achieve desired shades, especially in eyeliners, mascaras, and hair colorants.

Pros

Vibrant color payoff

Provides a deep, consistent black shade that is hard to achieve with natural alternatives, making it popular in eyeliners and mascaras.

Cost-effective

Synthetic dyes like CI 50420 are inexpensive to produce, keeping cosmetic prices lower for consumers.

Cons and cautions

Irritation risk

Can cause redness, itching, or stinging on sensitive skin, especially around the eyes or on compromised skin barriers.

Not a skincare active

This ingredient adds no moisturizing, anti-aging, or protective benefits—it's purely cosmetic.

Best for

  • People who want bold black makeup shades
  • Those without known sensitivities to synthetic dyes

Use caution if

  • Individuals with sensitive or reactive skin
  • Anyone with a known allergy to azo dyes

Usage tips

Patch test any product containing CI 50420 on a small area of skin before full use, especially near the eyes.
If you experience irritation, switch to products using iron oxides or charcoal as colorants.

Safety summary

CI 50420 is considered safe for most people at typical cosmetic levels, but it poses a moderate irritation risk for sensitive skin and a low risk of allergic reactions. Avoid if you have known dye allergies.

Research notes

Studies show that azo dyes like CI 50420 can cause contact dermatitis in susceptible individuals, but overall incidence is low. Regulatory bodies like the EU SCCS have reviewed it and found it safe within set limits.

Common label clues

Typical concentration
Typically less than 1% in rinse-off products; varies in leave-on products
Regulatory status
Approved for use in cosmetics in the EU and US within specified concentration limits, but always check local regulations as they vary.
Common uses
Makeup, Hair dye, Nail polish, Soap
Environmental note
Synthetic azo dyes can be persistent in the environment if not properly treated during wastewater processing, though cosmetic use is typically low-volume.

Good to know

  • CI 50420 is also known as Acid Black 1 and is used in some hair dyes as well as makeup.
  • In the EU, this dye is regulated and allowed in cosmetics at certain concentrations.

Common questions

What is CI 50420 in beauty products?

CI 50420 is a man-made black pigment used to give color to makeup, hair dyes, and other beauty products. It's not a skincare active ingredient—it's purely for appearance. While generally safe in small amounts, it can sometimes irritate sensitive skin or cause allergic reactions.

What does CI 50420 do in a beauty product?

In a cosmetic product, CI 50420 works by absorbing and reflecting light to create a black hue. It is mixed into formulations to achieve desired shades, especially in eyeliners, mascaras, and hair colorants.

Is CI 50420 safe for most people?

CI 50420 is considered safe for most people at typical cosmetic levels, but it poses a moderate irritation risk for sensitive skin and a low risk of allergic reactions. Avoid if you have known dye allergies.

Who should be careful with CI 50420?

Individuals with sensitive or reactive skin Anyone with a known allergy to azo dyes

Research sources

European Chemicals Agency (ECHA) - CI 50420OpenCosIng Database - CI 50420OpenPubMed - Azo dye contact allergyOpen

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.