Benzisothiazolinone
BIT · 1,2-Benzisothiazolin-3-one
What it is
An isothiazolinone-based biocidal preservative (CAS 2634-33-5) used to prevent microbial growth in water-based liquid formulations. Related to methylisothiazolinone (MIT) but structurally distinct.
In this product: Antimicrobial preservative, prevents microbial growth in liquid laundry and air care products.
Dose & route, what actually matters
Dermal (skin residue on fabric from laundered clothing; direct skin contact from air freshener spray). Inhalation during product use.
EUROPEAN UNION
EU CLP Regulation classifies BIT as Skin Sensitizer Category 1 (H317). Subject to EU Biocidal Products Regulation (BPR) 528/2012 for biocidal product uses. BIT is banned as a preservative in EU cosmetics; permitted in industrial/household product formulations subject to BPR authorization and risk assessment.
UNITED STATES
Permitted as a preservative in US household cleaning and air care products. No regulatory concentration ceiling or mandatory labeling requirement. Confirmed by name on Gain Original SmartLabel and Febreze Air Effects SmartLabel.
The evidence
EU CLP Regulation classifies BIT as Skin Sensitizer Category 1; isothiazolinones including BIT are subject to strict EU controls under the Biocidal Products Regulation (BPR 528/2012) and are banned as preservatives in EU cosmetics.
regulatory · 2017 · source
Australian Industrial Chemicals human health tier III assessment of isothiazolinones confirms BIT is classified as a skin sensitizer under EU CLP and is banned as a cosmetic preservative in the EU; no US equivalent restriction exists.
regulatory · 2023 · source
California Prop 65: Not listed on California Prop 65.
How to avoid it
Check laundry and air freshener labels for Benzisothiazolinone or BIT. Fragrance-free and clean-label detergent alternatives (e.g., those with EU Ecolabel) typically use alternative preservation systems.
Where it hides
Editorial analysis of publicly available regulatory and peer-reviewed sources. Not medical advice. We name our evidence and link it, including when an ingredient is fine.