Formaldehyde-based synthetic resins are used, for instance, to make cotton and viscose crease-resistant and make wool shrink-resistant.
In the Netherlands, manufacturers which use these resins must adhere to the Dutch Formaldehyde in Textile Commodities Act (Warenwetbesluit formaldehyde in textiel). This legislation limits the quantity of formaldehyde content in clothing. If this limit is exceeded, the garment is required to include the warning ‘wash before wearing’ on the product itself or on the product packaging. After a single wash, the limit for formaldehyde may no longer be exceeded.