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THIANTHOL

CAS 135-58-0
48

Safety score · 0–100

Moderate

Derived from EU CosIng regulatory status, PubChem hazard data and published research. How we score.

About

Thianthol (dimethylthiaxanthene) is an antimicrobial and skin conditioning agent historically used in psoriasis and eczema treatments. It has keratolytic and anti-pruritic properties but can be irritating to skin and is restricted in some regions due to ozone-layer concerns.

Thianthol (CAS 135-58-0) is a thiaxanthene derivative — specifically 1-dimethylthiaxanthene — not a true phenol despite its -thol suffix. It is structurally related to coal tar components and has been used since the early 20th century as a keratolytic and anti-parasitic agent. Thianthol's mechanism involves mitotic arrest in hyperproliferative keratinocytes and has mild anesthetic and anti-itch (anti-pruritic) properties. It is restricted in EU cosmetics under the 'ban substances that deplete the ozone layer' regulation (likely due to its structural class or manufacturing process involving halogenated or ozone-reactive chemistry). Skin irritation, erythema, and photosensitivity are known local adverse effects.

Function

ANTIMICROBIAL, SKIN CONDITIONING

Skin benefits

  • Keratolytic (exfoliating) effect useful for thickened skin conditions
  • Anti-pruritic (anti-itch) properties
  • Antimicrobial activity against skin pathogens
  • Historical use in psoriasis and eczema management

Known concerns

  • EU restriction for ozone-depleting potential — capped at limited concentrations
  • Known skin irritant — causes erythema and peeling
  • Photosensitization risk — UV exposure after application may cause burns
  • May cause allergic contact dermatitis
  • Limited availability in modern cosmetics due to regulation

References

EU

EU CosIng database

European Commission cosmetic ingredient registry — regulatory status, restrictions, authorised functions.

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This profile is for educational purposes and does not constitute medical advice. Regulatory status and scientific understanding evolve — always read the physical product label and consult a healthcare professional for personal concerns.