Is It Safe For A Man To Use On His Balls?
An Swedish study found links between mountain biking in men and decreased fertility and testicular abnormalities. The connection was the strong and repeated shocks to the scrotum and perineum (the area between the balls and ass) that the men were subjected to while biking.
However, compared to the bone-shaking vibrations of bouncing down a rough trail or jumping logs with a bike post stuck in your crotch, the minor tremors supplied by a typical vibrator are quite gentle and non-traumatic. The "Bo" and ""Tor"by Lelo are very popular men's toy the world over as well as the "P.2" cock ring by Laid.
However the overuse of a vibrator on the testicles is not advisable, but the occasional buzz on the balls shouldn't do any harm.