A radioseptic was a personal hygiene device used by the Enarans to sterilize their homes and hands, usually before eating. The devices were silver spheres, two or three of which were taken and rolled around in the palms of the hands.
The group known as the Regressives refused to use radioseptics, along with other advanced technology, contributing to the other Enarans' perception that they were a hazard to public health. Jareth, when speaking to Korenna Mirell, had mentioned the Regressives' refusal to use these devices and expressed his surprise that they hadn't started a plague due to non-use.
Neelix demonstrated the use of radioseptics to Chakotay in 2373. (VOY: "Remember")