Ingredient review
Acid Black 1
INCI: CI 28440
A safe, widely used synthetic dye in rinse-off cosmetics, but offers no skincare benefit.
In plain English
CI 28440 is a synthetic blue-black dye that gives color to products like shampoo, soap, and hair dye. It doesn't improve your skin or hair — it's purely for appearance. In the small amounts used in cosmetics, it's considered safe for most people, especially in products that are rinsed off quickly.
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
Acid Black 1 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 Black 1.
- 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 azo dye that produces a blue-black color. It is a purified version of a colorant originally derived from coal tar, now made in a lab.
How it works
It absorbs and reflects specific wavelengths of visible light, giving the product a blue-black tint. It does not interact with skin or hair biologically.
Pros
Vibrant color
Delivers a consistent, deep blue-black shade that doesn't fade easily in typical product formulations.
Low irritation risk
In rinse-off products, the risk of skin irritation is very low for the general population.
Cons and cautions
No functional benefit
CI 28440 is purely aesthetic — it doesn't moisturize, protect, or treat the skin or hair.
Potential allergen
A small number of people may experience allergic contact dermatitis, especially with prolonged skin contact.
Best for
- Anyone using rinse-off products like shampoo or soap
- People who want colorful cosmetic products
Use caution if
- Individuals with known sensitivity to azo dyes
- Those seeking skincare benefits from their colorants
Usage tips
Safety summary
CI 28440 is considered safe for use in cosmetics at typical concentrations, especially in rinse-off products. The main concern is rare allergic reactions in sensitive individuals.
Research notes
Studies show low acute toxicity and low skin irritation potential. Allergic reactions are uncommon but documented. Regulatory bodies worldwide approve its use with restrictions on concentration and product type.
Common label clues
- Typical concentration
- Very low, typically under 1%
- Regulatory status
- Approved as a color additive for cosmetics in the EU (Annex IV) and the US (FDA) for specific uses, mainly rinse-off products.
- Common uses
- Hair dyes, Soaps, Bath products, Shampoos
- Environmental note
- As a synthetic azo dye, it may persist in wastewater. Proper disposal and treatment are recommended to reduce environmental impact.
Good to know
- CI 28440 is approved for use in cosmetics in the EU, US, and many other regions.
- It is often listed simply as 'CI 28440' or 'Acid Black 1' on labels.
Common questions
What is Acid Black 1 in beauty products?
CI 28440 is a synthetic blue-black dye that gives color to products like shampoo, soap, and hair dye. It doesn't improve your skin or hair — it's purely for appearance. In the small amounts used in cosmetics, it's considered safe for most people, especially in products that are rinsed off quickly.
What does Acid Black 1 do in a beauty product?
It absorbs and reflects specific wavelengths of visible light, giving the product a blue-black tint. It does not interact with skin or hair biologically.
Is Acid Black 1 safe for most people?
CI 28440 is considered safe for use in cosmetics at typical concentrations, especially in rinse-off products. The main concern is rare allergic reactions in sensitive individuals.
Who should be careful with Acid Black 1?
Individuals with known sensitivity to azo dyes Those seeking skincare benefits from their colorants
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.