Rebbe Nachman said: Mikvah is not the least bit harmful. Any doctor who says it is, is no doctor at all.

On the contrary, immersing in a mikvah is very beneficial for the body’s health. This is because there are many small pores in the human body, sweat pores, through which the perspiration leaves a person. They need to be open, because if the sweat pores are blocked a person can become weak and fall ill, God forbid.

Immersing in water opens the sweat pores, which is very beneficial for the body’s health. This is so long as the water is not excessively cold, because in that case water closes up the aforementioned pores. But when not very cold, immersing in the water is very beneficial.

It has also already been explained that devotions and self-mortification (called horivani) cause no harm. Whomever the devotions or the self-mortification does harm, it is only because of pride.