Manufacturers of sanitary pads and masks will be required to display materials used in the making of their products on packaging from later this year, the government said Thursday.

The announcement by the Korea Food and Drug Administration comes months after a local activist group claimed that 6 out of 10 users of the controversial Lilian brand sanitary napkins have experienced menstrual disorders, including unstable cycles and painful periods, due to possible side effects of chemicals.

The Ministry of Food and Drug Safety last year examined 666 sanitary pads manufactured or imported since 2014 for volatile organic compounds to see if they contain any harmful chemicals and said none pose health risks to women.