Ingredient review
CI 42100
INCI: CI 42100
CI 42100 is a safe, widely used synthetic green dye that adds color to cosmetics but offers no skincare benefits.
In plain English
CI 42100 is a man-made green dye used to make products look more appealing. It doesn't treat or improve your skin—it's purely cosmetic. Regulatory bodies consider it safe for use in small amounts in rinse-off and some leave-on products.
Review score
Safety, usefulness, and evidence
Useful in the right context, but not low-maintenance
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Read the cautions before using
CI 42100 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 CI 42100.
- 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
A synthetic organic compound from the anthraquinone family, used as a green colorant in cosmetics and personal care products.
How it works
It absorbs and reflects specific wavelengths of light to produce a green color. It is mixed into product formulas to achieve a desired shade, without affecting the product's performance or skin feel.
Pros
Stable color
Provides a consistent, fade-resistant green shade across different product types and pH levels.
Regulatory approval
Approved by the FDA, EU, and other major regulators for use in cosmetics at safe levels.
Cons and cautions
No skin benefit
Purely aesthetic; does not moisturize, protect, or improve skin health.
Potential allergen
While rare, some individuals may experience contact dermatitis or irritation from synthetic dyes.
Best for
- Anyone who wants a green-tinted cosmetic product
- People without known sensitivities to synthetic dyes
Use caution if
- Individuals with known allergies to synthetic colorants or anthraquinone compounds
Usage tips
Safety summary
CI 42100 is considered safe for cosmetic use at typical concentrations. Rare allergic reactions have been reported, but overall risk is low.
Research notes
Studies and regulatory reviews support its safety in cosmetics. No significant health concerns have been identified at authorized usage levels.
Common label clues
- Typical concentration
- Very low, typically less than 1%
- Regulatory status
- Approved for use in cosmetics by the FDA (as D&C Green No. 5) and the European Commission (as CI 42100) within specified concentration limits.
- Common uses
- Shampoos, Soaps, Bath products, Eye shadows
- Environmental note
- As a synthetic dye, it may not be biodegradable and could contribute to water pollution if not properly treated in wastewater.
Good to know
- CI 42100 is also known as D&C Green No. 5 in the US and Acid Green 25 in other contexts.
- It is often used in combination with other colorants to create custom shades.
Common questions
What is CI 42100 in beauty products?
CI 42100 is a man-made green dye used to make products look more appealing. It doesn't treat or improve your skin—it's purely cosmetic. Regulatory bodies consider it safe for use in small amounts in rinse-off and some leave-on products.
What does CI 42100 do in a beauty product?
It absorbs and reflects specific wavelengths of light to produce a green color. It is mixed into product formulas to achieve a desired shade, without affecting the product's performance or skin feel.
Is CI 42100 safe for most people?
CI 42100 is considered safe for cosmetic use at typical concentrations. Rare allergic reactions have been reported, but overall risk is low.
Who should be careful with CI 42100?
Individuals with known allergies to synthetic colorants or anthraquinone compounds
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.