Heat-based contraception

An experimental male contraceptive method involves heating the testicles so that they cannot produce sperm. Sperm are best produced at a temperature slightly below body temperature. The muscles around a man's scrotum involuntarily tighten if the man's body temperature drops, and they loosen, allowing the testes to hang, if the body temperature rises. This is the body's way of keeping the sperm at an ideal temperature. Limited research has shown that raising the temperature of the scrotum above body temperature, even for short periods of time, can affect fertility for months.

Methods used include hot water applied to the scrotum, heat generated by ultrasound, and artificial cryptorchidism (holding the testicles inside the abdomen) using specialized briefs. Initial experiments suggest it is effective, safe, and reversible, though there have not been long-term studies to determine if it has any side effects on the body or quality of sperm after reversal. The optimal heat level and time period of exposure are not known.

The method has a long history in middle-eastern countries, particularly Turkey.