Menstrual cups are generally not so harmful but it comes up with a little risk and complications that may occur in rare cases. Minor symptoms include irritation that may happen for various reasons including - 1) inserting cup without using a proper lubricant, wearing cup of wrong size, and if the cup is not cleaned properly. It is recommended to read the manufacturer's guidelines before its use. 2) infection is one of the rare complications of using a menstrual cup. In the majority of cases, the infection travels from your hands to the menstrual cup and eventually to the body. Reduce such risks by washing your hands by warm water and using proper antibacterial soaps before touching the menstrual cup. 3) rare but the most serious complication of using menstrual cups is toxic shock syndrome (tss). This is a bacterial infection and it occurs when pre-existing bacteria (staphylococcus or streptococcus), that stays on your skin, nose, or mouth, is pushed deep inside your body.