Two product types are of particular importance in contact allergy to polyester resin: powder paints cured by heat with TGIC as the cross-linker, and car putties. Car putties are used not only in repair car painting, but also in some industrial trades to smoothen surfaces before painting. As commercial patch test substances of polyester resin putties are lacking, patients' own products need to be tested. Cobalt salts are used in several types of polyester resin product as accelerators, and these must be considered as a possible cause of cobalt sensitization.