4-Nitro-o-Phenylenediamine

4-Nitro-o-Phenylenediamine molecular structure
molecular structure · PubChem
AKA: 99-56-9, 4-Nitro-1, 2-phenylenediamine, 1, 2-Diamino-4-nitrobenzene, 2-Amino-4-nitroaniline, 2-diaminobenzene, P-Nitro-o-phenylenediamine, 3, 4-Diaminonitrobenzene, 2-Benzenediamine, 2-benzenediamine
Allergen Warning
⚠️ PPD (Hair Dye)
Synthetic
Safety Concern
Not Clean
4-nitro-o-phenylenediamine (CI 76020)
Solubility less than 1 mg/mL at 68.9 °F (NTP, 1992)
Formula
C6H7N3O2
Mol. Weight
153.14
CAS #
99-56-9
Form
Liquid
State
4-nitro-o-phenylenediamine appears as dark red needles or red solid. (NTP, 1992)
Functions
Hair Dyeing
Reduces Inflammation
Antioxidant Protection
Fights Bacteria
Colors Hair
Traditional Use
Synthetic azo dye developed in the early 20th century for use as a hair colorant. Part of the family of coal tar-derived compounds that revolutionized permanent hair color formulation.
EWG
4
CIR
Safe as used
Pregnancy
No
CIR Safety Findings
Not a Sensitizer
medical-approval
all-shades-safe
Regulatory Status
USA✔ permitted
EU✔ permitted
JAPAN✔ permitted
CANADA✔ permitted
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
No
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR