Hydroquinone

AKA: 123-31-9, Benzene-1, 4-diol, 1, 4-benzenediol, Quinol, 4-Dihydroxybenzene, P-Hydroquinone, P-Hydroxyphenol, P-Benzenediol, P-Dihydroxybenzene
Synthetic
Not Clean
OriginHydroquinone is a benzene derivative synthesized from aromatic hydrocarbon precursors through organic chemistry processes. It is produced by oxidation of hydrobenzene or through catalytic processes involving benzene and hydrogen peroxide.
Hydroquinone, also benzene-1,4-diol, is an aromatic organic compound which is a type of phenol. Hydroquinone is commonly used as a biomarker for benzene exposure. The presence of hydroquinone in normal individuals stems mainly from direct dietary ingestion, catabolism of tyrosine and other substrates by gut bacteria, ingestion of arbutin containing foods, cigarette smoking, and the use of some over-the-counter medicines. In human medicine, hydroquinone is used as a topical application in skin whitening to reduce the color of skin. In 2006, the United States Food and Drug Administration revoked its previous approval of hydroquinone and proposed a ban on all over-the-counter preparations. The FDA stated that hydroquinone cannot be ruled out as a potential carcinogen. This conclusion was reached based on the extent of absorption in humans and the incidence of neoplasms in rats in several studies where adult rats were found to have increased rates of tumours, including thyroid follicular c
Solubility 10 to 50 mg/mL at 68 °F (NTP, 1992)
Formula
C6H6O2
Mol. Weight
110.11
CAS #
123-31-9
Form
Powder
State
Hydroquinone appears as light colored crystals or solutions. May irritate the skin, eyes and mucous membranes. Mildly toxic by ingestion or skin absorption.
Skin Types
●all-skin-types
Best For
Hyperpigmentation
Pregnancy & Breastfeeding Safe
No
Functions
Light Stabilizer
Shields from UV damage
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed3 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
EWG
8
CIR
Safe as used
Pregnancy
No
CIR Safety Findings
Mixed Phototoxicity Results
Both phototoxic and non-phototoxic results in the CIR safety assessment (CIR 182)
Eye Irritant in Testing
1 study / 1 irritating / reactions mild (CIR 182)
Mixed Skin Irritation Results
12 studies / 10 irritating / 1 mixed / 1 not irritating / reactions slight to severe (CIR 86 and 182 and 551 and 647)
Mixed Sensitization Results
13 studies / 8 sensitizing / 1 mixed / 4 not sensitizing / plus 4 case reports (CIR 86 and 182 and 551 and 647)
Dermal Absorption 26–66%
6 results from human / in vitro tests in the CIR safety assessment (CIR 551 and 647)
Concentration Guide
0%50%100%
Reg. limit 0.02%
CIR's newest survey reports no concentration of use.
CIR · 2013 survey
EU regulatory limit: 0.02%. - For professional use only - Avoid skin contact - Read directions for use carefully Source: EU Cosmetics Regulation (EC) 1223/2009, Annex III (Restricted Substances), Entry 14.
Regulatory Status
USA✔ permitted
EU✔ permitted
JAPAN✔ permitted
CANADA✔ permitted
🧂Conflict of interest.
Verified Jun 2026 · 🧪 = conflict
Data: PubChem · CosIng · EWG · CIR