Observations concerning contact dermatitis to derivatives of isothiazolin-3-one are reported. A systematic review of the literature of previously published cases is reported. A verified contact dermatitis to benzisothiazolin-3-one of a laborer in a rubber factory is discussed. Another case of occupational dermatitis concerns an allergy to a commercial product, containing 2-n-octyl-4-isothiazolin-3-one as a preservative and utilized by shoe factory workers. Additionally, cases of an allergy to cosmetic preparations, containing a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, are elaborated.