Common Name(s): P-butylresorcinol,rucinol

CAS Number: 18979-61-8

DESCRIPTION

What It Does: Provides exceptional brightening through the most potent tyrosinase inhibition of any commonly used cosmetic brightening agent.

Why It's Used: The most potent tyrosinase inhibitor available in cosmetics – exceptional for refractory hyperpigmentation and melasma where standard brighteners provide insufficient efficacy.

How It Works: Resorcinol backbone competitively inhibits both tyrosine hydroxylase (reaction 1) and dopa oxidase (reaction 2) activities of tyrosinase. n-butyl chain provides superior membrane affinity for enhanced delivery to melanosomes.

Typically Found In: High-potency brightening serums,melasma treatments,stubborn hyperpigmentation products

TECHNICAL DETAILS

Primary Category: Active ingredient – resorcinol tyrosinase inhibitor

Secondary Functions: Dual tyrosinase reaction inhibition,potent brightening

Application Areas:

Typical Concentration Range: 0.1%–1%

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Synthetic or plant-derived.

SKIN COMPATIBILITY

Irritancy Rating: 2/5 – low to moderate

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Use with spf; introduce gradually. photosensitizing.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Excellent safety profile. use with spf for maximum efficacy. ewg score: 1.

Works Well With: Niacinamide,vitamin c,alpha-arbutin,tranexamic acid,spf

Avoid Combining With: No significant incompatibilities

SCIENTIFIC NOTE

4-butylresorcinol's inhibition of both tyrosinase catalytic reactions (tyrosine→dopa and dopa→dopaquinoneoxidase) is unique among common brighteners. most tyrosinase inhibitors only block the first reaction (tyrosine→dopa). blocking both steps provides more complete melanin biosynthesis inhibition.

Last Verified: Cosing database,choi et al. 4-butylresorcinol study,sccs opinion on butylresorcinol

Primary Sources: 2026-03-12