Isothiazolinones

Isothiazolinones are a family of sulfur- and nitrogen-containing heterocyclic compounds characterized by a five-membered isothiazolinone ring. Common members include methylisothiazolinone (MI), chloromethylisothiazolinone (CMIT), benzisothiazolinone (BIT) and octylisothiazolinone (OIT). CMIT is often used in combination with MI as a broad-spectrum antimicrobial mixture.

These compounds act as biocides by reacting with thiol groups in microbial enzymes and proteins, inhibiting essential cellular processes and causing cell death. Because of their effectiveness at low concentrations they are widely used as preservatives in water-based products such as paints, adhesives, personal care products, household cleaners, industrial cooling systems and paper.

Concerns about human health have focused on skin sensitization and contact allergy. Reports of allergic contact dermatitis, particularly linked to MI in personal care products, prompted regulatory reviews and restrictions in several jurisdictions; many countries now limit or ban certain isothiazolinones in leave-on cosmetics and set concentration limits for rinse-off products. Occupational exposure in industrial settings is also monitored.

Environmental toxicity can be significant for aquatic organisms, so effluent controls and consideration of biodegradability are important in industrial use. Alternatives used where sensitization or environmental risk is unacceptable include different preservative classes or formulation strategies to avoid biocidal additives. Research continues on safer preservatives and exposure reduction.