Formaldehyde-based synthetic resins are used, for instance, to make cotton and viscose crease-resistant and make wool shrink-resistant. In the Netherlands, manufacturers that use therse resins must adhere to the Dutch Formaldehyde in Textile Commodities Act (Warenwetbesluit formaldehyde in textiel). This Act specifies the limit value of formaldehyde content in clothing. When it is exceeded, it is required to include the warning ‘wash before wearing’ on the product itself or on the product packaging. After a single washing, the product must no longer exceed the limit value for formaldehyde.