The invention provides a method for preventing discoloration of pyrithione-containing materials, in particular plastic materials or other material such as paints, coatings, adhesives or textiles which are exposed to an outdoor environment. The method is likewise suited for preventing discoloration of other pyrithione-containing materials such as personal care compositions like shampoos. A discoloration inhibitor that includes dehydroacetic acid or a salt thereof is added to the pyrithione-containing material. The discoloration is prevented without the addition of a cyclic organic phosphoric acid ester or an organic phosphite. Use of the discoloration inhibitor does not interfere with the antimicrobial effect of the pyrithione.
