Men are tanning their testicles in a bid to become more macho.
Tucker Carlson revealed a trailer about a testicle tanning documentary
The practice, which is also known as red-light therapy, involves blasting the private parts with light to boost testosterone levels.
Testicle tanning has taken off recently after it was promoted by US news presenter Tucker Carlson in a trailer for the documentary 'The End of Men' - a film about the dip in male testosterone production.
It is believed that the bizarre therapy is growing in demand, with some claiming that it strengthens blood vessels and improves blood flow.
However, doctors are unimpressed with the tanning of the testicles - a concept that first emerged with the study of five men in 1939.
Dr. Asif Muneer, a consultant urological surgeon and andrologist, said: "What is testicle tanning? There is no scientific evidence that this has any benefit."