Ingredient review

Acid Blue 9

INCI: CI 73000

A widely used synthetic blue dye that adds color to products but offers no skincare benefits.

beautyskincarecolorant

In plain English

CI 73000 is a synthetic blue dye, also known as Acid Blue 9 or FD&C Blue No. 1. It is added to cosmetics and personal care items to give them a blue color. It does not improve skin health or function—it is purely for appearance. Regulatory bodies consider it safe for use in cosmetics at the low levels typically found in products.

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.

Risk flags are low for most users, though the finished product can still irritate.

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

Quick decision guide

Useful, but context matters

Acid Blue 9 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 Blue 9.
  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

A water-soluble synthetic dye from the triphenylmethane family, produced from petroleum-derived raw materials.

How it works

It absorbs and reflects light in the blue spectrum, imparting a blue color to the product. It does not interact with the skin or hair beyond surface contact.

Pros

Vibrant color

Provides a bright, consistent blue shade that is stable in water-based formulas.

Regulatory approval

Approved by the FDA and EU for use in cosmetics at safe levels.

Cons and cautions

No skin benefit

Adds only color—does not moisturize, protect, or improve skin health.

Potential staining

In high concentrations or with prolonged contact, it may temporarily stain skin or fabrics.

Best for

  • Anyone who wants a blue-tinted cosmetic product
  • Formulators needing a stable blue colorant

Use caution if

  • People with known sensitivity to synthetic dyes (rare)
  • Those seeking purely natural or organic products

Usage tips

Use in rinse-off products like shampoos to minimize skin contact time.
Check product labels if you prefer to avoid synthetic dyes.

Safety summary

Generally recognized as safe for cosmetic use at low concentrations. Rare allergic reactions have been reported, but it is well-tolerated by most people.

Research notes

Studies confirm low acute toxicity and low skin irritation potential. Long-term safety data supports its use in cosmetics at regulated levels.

Common label clues

Typical concentration
Very low, typically less than 1%
Regulatory status
Approved for use in cosmetics in the US (FDA) and EU (EC) within specified concentration limits.
Common uses
Shampoos, Soaps, Bath products, Lotions, Makeup
Environmental note
As a synthetic dye, it is not biodegradable and may persist in water systems if not properly treated.

Good to know

  • CI 73000 is the same as FD&C Blue No. 1, which is also used in food and drugs.
  • It is often combined with other dyes to create custom shades.

Common questions

What is Acid Blue 9 in beauty products?

CI 73000 is a synthetic blue dye, also known as Acid Blue 9 or FD&C Blue No. 1. It is added to cosmetics and personal care items to give them a blue color. It does not improve skin health or function—it is purely for appearance. Regulatory bodies consider it safe for use in cosmetics at the low levels typically found in products.

What does Acid Blue 9 do in a beauty product?

It absorbs and reflects light in the blue spectrum, imparting a blue color to the product. It does not interact with the skin or hair beyond surface contact.

Is Acid Blue 9 safe for most people?

Generally recognized as safe for cosmetic use at low concentrations. Rare allergic reactions have been reported, but it is well-tolerated by most people.

Who should be careful with Acid Blue 9?

People with known sensitivity to synthetic dyes (rare) Those seeking purely natural or organic products

Research sources

FDA Color Additive Status ListOpenCosIng Database - CI 73000OpenPubChem - Acid Blue 9Open

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.