MonthlyCup’s guide says to follow the supplied instructions and boil before first use and between periods as instructed. It also says to dry the cup fully and store it with air circulation.
Before your first try, read the instruction manual without rushing. Put the manual somewhere easy to reach, wash your hands, and give yourself time. Cups can take practice, so a calm routine matters.
MonthlyCup’s guide says to replace damaged, sticky or noticeably changed silicone. Do not keep using a cup that has visibly changed condition.