Is it okay Islamically to use a menstrual cup as a more eco friendly alternative to sanitary towels?
In the name of Allah, the Inspirer of truth
Menstrual cups are like tampons, in that they are inserted in the vagina to contain period fluid. It is disliked (makruh) to insert anything into the internal part of the vagina. It is preferable to use sanitary liners/pads.
For non-virgins, who have irregular spotting/bleeding (istihada), it is permissible to use a menstrual cup or tampon to block the flow of blood. This will allow them to maintain purity during their ritual worship.
For virgins, it is discouraged to use either product. The reasoning behind the prohibition is to protect young girls from self-exploration of the private areas, which may lead to sinful behavior. This prohibition also extends to non-virgin women that feel the use of these products may make them susceptible to female masturbation.
And Allah knows best.