p-Phenylenediamine
Caution
Official INCI name
The key ingredient in most permanent dark hair dyes and a potent allergen — patch test every time, and never use it on skin ("black henna").
What it does
Colorant. Pigments and dyes (often listed as CI numbers).
Worth knowing
Can cause contact allergy that, once developed, returns on every exposure.
Also written as
Scans recognise it under every one of these names.
PPD
“p-Phenylenediamine” is its name in the EU glossary of common ingredient names (no. 23226), the names labels in the EU must use. © European Union, EUR-Lex.