Common Name(s): Ppd,1,4-diaminobenzene,para-phenylenediamine

CAS Number: 106-50-3

DESCRIPTION

What It Does: Provides the primary oxidative hair colouring intermediate for permanent hair colour systems.

Why It's Used: The standard oxidative hair dye primary – ppd is the most reactive and widely used primary intermediate providing the broadest colour range in permanent hair colouring.

How It Works: Ppd is oxidised by h2o2 to form a diamine quinonediimine that couples with secondary intermediates (couplers) to form large, permanently coloured indophenol, indoaniline, or bandrowski's base molecules. oxidised coupling products are too large to diffuse out through the swollen hair cuticle, providing permanence.

Typically Found In: Permanent hair colours

TECHNICAL DETAILS

Primary Category: Hair colourant – primary oxidative dye

Secondary Functions: Skin conditioning

Application Areas:

Typical Concentration Range: 0.1%–3%

SOURCING & ETHICS

Vegan Status: Conditional - supplier confirmation required

Halal Status: Unverified - supplier confirmation required

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier. [audit 2026-07-29 rev2: the record's own source_notes does not assert a non-animal origin, or instructs the reader to verify with the supplier; "yes" asserts knowledge the record does not hold. determination requires shariah-panel sign-off.]

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu annex iii restricted: max 2% after mixing in ready-to-use product. requires mandatory consumer allergy warning. ppd is the most common cause of allergic contact dermatitis from hair colouring. patch test 48 hours before use.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Ppd's oxidative coupling mechanism makes it both effective and allergenic: the quinonediimine intermediate that couples with dye couplers also forms hapten conjugates with skin proteins when it penetrates the scalp. these protein conjugates trigger type iv (delayed-type) hypersensitivity in 1-13% of hair colour users, making ppd allergy one of the most common occupational dermatoses in hairdressers.

Last Verified: 2026-03-12

Primary Sources: Cosing database,eu annex iii hair dye restriction,cir safety assessment