Cosmetics · Quasi-drug actives
4-n-Butylresorcinol
4-n-ブチルレゾルシノール (4-n-Buchiru rezorushinōru)
Also known as: Butylresorcinol, POLA markets a preparation as Rucinol®
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| Category | Cosmetics |
|---|---|
| INCI name | Butylresorcinol↗ |
| Japanese labeling name | 4-n-ブチルレゾルシノール |
| Common Japanese notations | 4-n-ブチルレゾルシノール |
| CAS number | 18979-61-8↗ |
| Origin | Synthetic (resorcinol derivative) |
| Typical functions | Quasi-drug whitening (medicated bihaku) active |
| Regulatory status in Japan | Approved as a quasi-drug (医薬部外品) whitening active by Japan's 厚生労働省 (Ministry of Health, Labour and Welfare) in 1998. Approval applied for by POLA Chemical Industries. |
4-n-Butylresorcinol is a synthetic resorcinol derivative approved as a quasi-drug whitening active in Japan in 1998. POLA Chemical Industries, the company that applied for and received the approval, markets its preparation of the ingredient under the registered trademark Rucinol®.
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Classification
Tags below link to other ingredients sharing the same attribute, so you can pivot from one ingredient to its peers.
Product applications
Functions
Regulatory tags
Origin
Common OEM product categories
Finished-product categories where Japanese OEM manufacturers commonly formulate with this ingredient.
- Medicated whitening lines (薬用美白) marketed under Kanebo brands
- Quasi-drug serums and lotions targeting dark spots
- Quasi-drug creams for hyperpigmentation
- Brightening face masks (medicated)
Ingredient profile
4-n-Butylresorcinol is the n-butyl-substituted resorcinol with the structure 4-n-butyl-1,3-benzenediol. It functions as a tyrosinase inhibitor in the melanin biosynthesis pathway, the basis for its quasi-drug whitening application.
OEM applications
Within Japan, the ingredient's commercial use is concentrated in POLA's medicated whitening lines marketed under Rucinol®.
Regulatory classification in Japan
Approved by 厚生労働省 (Ministry of Health, Labour and Welfare) as a quasi-drug whitening active in 1998 following POLA Chemical Industries' application. Permits the standard medicated whitening claim wording.
Regulatory classification in other markets
| EU | Butylresorcinol is listed in CosIng. Permitted for cosmetic use within applicable concentration ranges. |
|---|---|
| USA | INCI recognized. |
| China | Cosmetic use should be verified against current IECIC listings; resorcinol-family ingredients may have specific concentration considerations. |
| Korea | Permitted under KFDA / MFDS for cosmetic use. |
Market reference formulations
Example products are concentrated in POLA's branded medicated whitening lines. Specific SKU listings will be added after each product's current full ingredient list has been verified.
All brand names and product names referenced anywhere on this site are the property of their respective owners. Example entries are provided for informational purposes only and do not imply endorsement.
Alternative ingredients
Related ingredients commonly evaluated as substitutes.
Quick answers
- What is 4-n-Butylresorcinol?
- 4-n-Butylresorcinol is a synthetic resorcinol derivative approved as a quasi-drug whitening active in Japan in 1998. POLA Chemical Industries, the company that applied for and received the approval, markets its preparation of the ingredient under the registered trademark Rucinol®.
- What is the regulatory status of 4-n-Butylresorcinol in Japan?
- Approved as a quasi-drug (医薬部外品) whitening active by Japan's 厚生労働省 (Ministry of Health, Labour and Welfare) in 1998. Approval applied for by POLA Chemical Industries.
- What products typically use 4-n-Butylresorcinol?
- Medicated whitening lines (薬用美白) marketed under Kanebo brands / Quasi-drug serums and lotions targeting dark spots / Quasi-drug creams for hyperpigmentation / Brightening face masks (medicated)
- Where does 4-n-Butylresorcinol come from?
- Synthetic (resorcinol derivative)
- What is the INCI / JSCI labeling name for 4-n-Butylresorcinol?
- INCI: Butylresorcinol / JSCI: 4-n-ブチルレゾルシノール
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Regulatory guidance
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FAQ for OEM buyers
Q. What is the regulatory status of 4-n-butylresorcinol in Japan?
It is approved as a quasi-drug whitening active by 厚生労働省 (Ministry of Health, Labour and Welfare) under the brand name Rucinol; finished products using it must be filed as quasi-drugs, not general cosmetics.
Sources · Last reviewed: 2026-04-26
- 厚生労働省 (Ministry of Health, Labour and Welfare) — quasi-drug approval lists (medicated whitening actives)
Q. Is butylresorcinol available to third-party OEMs or only POLA?
Rucinol is a POLA-developed and trademarked active; commercial supply for finished products has been concentrated within POLA's lines, though the molecule itself is also used outside Japan (e.g., EU brightening cosmetics) at varying purity grades.
Sources · Last reviewed: 2026-04-26
- Industry knowledge — POLA Rucinol® brand and licensing
Industry-knowledge claim — not yet pinned to a single primary source
Q. How does butylresorcinol compare with other tyrosinase inhibitors for OEM positioning?
Published in-vitro studies have reported it as a potent tyrosinase inhibitor relative to arbutin and kojic acid, which is the standard comparative claim for premium positioning. Final efficacy in finished products depends on formulation and exposure.
Sources · Last reviewed: 2026-04-26
- Peer-reviewed literature — tyrosinase inhibition studies (PubMed, butylresorcinol)
Q. What is the typical use level and stability profile?
Approved quasi-drug use levels are typically ≤0.3%; the molecule is sensitive to oxidation and discolouration, so opaque packaging and chelating agents are commonly specified.
Sources · Last reviewed: 2026-04-26
- Industry knowledge — resorcinol-class active formulation
Industry-knowledge claim — not yet pinned to a single primary source
Use cases
Medicated whitening cream (薬用美白クリーム)
- Positioning
- Premium Rucinol® POLA line
- Typical usage level
- ≤0.3% as quasi-drug active
- Formulation notes
- Often paired with antioxidants and anti-irritants; opaque/airless packaging recommended.
Sources
- Industry knowledge — POLA Rucinol® product lineup
Industry-knowledge claim — not yet pinned to a single primary source
Spot-targeted serum
- Positioning
- Targeted dark-area / hyperpigmentation treatment
- Formulation notes
- Higher-strength leave-on serum; quasi-drug registration required for whitening claims.
Sources
- Industry knowledge — premium spot-care category
Industry-knowledge claim — not yet pinned to a single primary source
Brightening cosmetic (non-whitening positioning, EU/global)
- Positioning
- EU/Asia general cosmetic positioned as brightening (no medicated claim)
- Formulation notes
- Used outside Japan at lower levels in cosmetic-claim products without quasi-drug filing.
Sources
- Industry knowledge — global brightening category
Industry-knowledge claim — not yet pinned to a single primary source
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Official regulatory databases
External links to public Japanese / international regulatory authorities. We are not affiliated.
References
- Japan 医薬品医療機器総合機構 PMDA (Pharmaceuticals and Medical Devices Agency) — quasi-drug active ingredient approval registry
- POLA Chemical Industries corporate publications referencing Rucinol®
Last updated: 2026-04-22. Ingredient entries are reviewed at least annually against current regulatory listings.