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Annex II Entry 352 15/10/2010

Bithionol (INN)

Bithionol (INN) is listed in Annex II as a prohibited substance for cosmetic products placed on the EU market.

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Prohibited substance— Annex II, EU Regulation 1223/2009
Entry: 352

Chemical identity and properties

PubChem 2D chemical structure for CAS 97-18-7
CAS 97-18-7PubChem CID 2406

Bithionol

Bithionol is an aryl sulfide that is diphenyl sulfide in which each phenyl group is substituted at position 2 by hydroxy and at positions 3 and 5 by chlorine. A fungicide and anthelmintic, it was used in various topical drug products for the treatment of liver flukes, but withdrawn after being shown to be a potent photosensitizer with the potential to cause serious skin disorders. It has a role as an antiplatyhelmintic drug and an antifungal agrochemical. It is a dichlorobenzene, a polyphenol, an aryl sulfide, an organochlorine pesticide, a bridged diphenyl fungicide and a bridged diphenyl antifungal drug. — ChEBI

IUPAC name
2,4-dichloro-6-(3,5-dichloro-2-hydroxyphenyl)sulfanylphenol
Molecular formula
C12H6Cl4O2S
Molecular weight
356.0 g/mol
Exact mass
355.881311 Da
XLogP3
5.8
Topological polar surface area
65.8 Ų
Hydrogen-bond donors
2
Hydrogen-bond acceptors
3
Covalent units
1
Defined stereocentres
0

Also known as

BithinLorothidol2,2'-Thiobis(4,6-dichlorophenol)ActamerBitionolBidiphenBisoxyphenLorothiodol
16 more reported names
Bithionol sulfideBithionolateNeopellisBitinVancide BLTKhsdUsaf B-222-Hydroxy-3,5-dichlorophenyl sulfideBithionolumBis(2-hydroxy-3,5-dichlorophenyl) sulfideBis(3,5-dichloro-2-hydroxyphenyl) sulfide2,2'-sulfanediylbis(4,6-dichlorophenol)2-Hydroxy-3,5-dichlorophenyl sulphide2,2'-Dihydroxy-3,3',5,5'-tetrachlorodiphenyl sulfideCP 3438NCI-C60628
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External database identifiers

Retrieved from NIH PubChem on 2026-08-31 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Chemical name

Bithionol (INN)

Chemical / IUPAC name

2,2'-Thiobis(4,6-dichlorophenol)

Regulatory information

Regulation

(EC) 2009/1223

See every entry this act set

Key data

CAS
97-18-7
EC
202-565-0
Annex
II
Entry number
352

Direct matches are limited for this record, so nearby entries from Annex II are shown as well.

What Annex II means for Bithionol (INN)

Bithionol (INN) is listed as a prohibited substance under Annex II of EU Cosmetics Regulation 1223/2009 and must not be intentionally added. Article 17 separately addresses unintended small quantities that are technically unavoidable under good manufacturing practice and compatible with the Article 3 safety requirement.

Formulators must screen their ingredients and raw materials to ensure none contain this substance. Suppliers should provide documentation confirming absence when requested.

The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Verify this substance is absent from all raw materials and finished formulations.
  • Request absence confirmation or CoA from raw material suppliers.
  • Document the screening result in the Product Information File (PIF).

Frequently asked questions

Yes. Bithionol (INN) is listed in Annex II of EU Cosmetics Regulation 1223/2009 and is prohibited as an intentionally added cosmetic ingredient. Article 17 provides a narrow exception for unintended small quantities that are technically unavoidable under good manufacturing practice, provided the product remains safe under Article 3.

CAS 97-18-7 is the unique numerical identifier assigned to Bithionol (INN) by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex II record Bithionol (INN)

This page summarizes one Annex II record for Bithionol (INN) from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex II conditions for Bithionol (INN), but confirm any final regulatory decision against the current official annex wording and source files.

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