CI 42090 (FD&C Blue No. 1 Or D&C Blue No. 4)

What is CI 42090 (FD&C Blue No. 1 Or D&C Blue No. 4)?

CI 42090, known as FD&C Blue No. 1 or D&C Blue No. 4, is a synthetic organic colorant derived from triarylmethane. This water-soluble dye appears as a bright blue powder or liquid, certified for purity in cosmetic-grade forms. Primarily employed in makeup, shampoos, conditioners, and hair dyes, it functions by selectively absorbing specific light wavelengths, imparting a stable blue hue to formulations. In products, it enables precise shade matching across batches, enhances visual appeal in rinse-off and leave-on items, and integrates into hair coloring systems for temporary or semi-permanent effects. Regulatory bodies like the FDA approve it for external use, with restrictions on eye-area applications in some cases, ensuring it disperses evenly without altering product texture.

Comedogenic Rating 0/5 Low risk of clogging pores
EWG Safety Rating 2-7 View on EWG →
PubChem View on PubChem →

Roles in Formulation

This ingredient serves the following purposes in cosmetic formulations:

Colorant
Provides or corrects color using dyes or pigments, helping achieve a consistent shade and visual appearance across batches and throughout wear.
Hair dyeing
Supports chemical color change of hair (e.g., oxidative dye development or bleaching), enabling shade transformation through controlled reactions on the fiber.
Hair colorant
Delivers hair color through dyes and/or pigments (direct or oxidative systems), producing a visible shade change and supporting coverage and longevity.

Benefits

Delivers consistent blue pigmentation for uniform product appearance.

Supports reliable color in hair dyes and cosmetics across production batches.

Non-comedogenic, suitable for formulations targeting pore-friendly options.

Who It's For

A quick guide for who this ingredient may suit (and who should be cautious).

Who May Benefit Who Should Avoid
Users seeking vibrant color in eye makeup or rinse-off cleansers.
Those with known sensitivities to synthetic dyes.
Individuals coloring hair with blue shades for creative looks.
People experiencing allergic reactions to triarylmethane colorants.
People with acne-prone skin preferring non-pore-clogging colorants.
Users prone to contact dermatitis from certified color additives.

Safety Notes

  • Approved for cosmetic use by FDA with certified purity requirements.
  • Rated low to moderate concern by EWG based on potential impurities.

Frequently Asked Questions about CI 42090 (FD&C Blue No. 1 Or D&C Blue No. 4)

What is CI 42090 used for in cosmetics?

It acts as a colorant in makeup, shampoos, and hair products to provide stable blue shades.

Is CI 42090 safe for skin?

Certified forms are approved for external use, with low comedogenic potential.

Can it cause allergies?

Rare hypersensitivity occurs; patch test recommended for sensitive users.