Unsatisfied and prolonged sexual arousal in males can cause a condition known as blue balls. This is a slang term that is believed to have originated in the U.S. around 1916.
Fluid and blood congestion in the testicles and prostate region can cause discomfort and even pain in these regions. This condition is called blue balls. Medical doctors call this epididymal hypertension and not all males experience this problem.
During sexual arousal in the male, blood flows into the groin region. This results in dilation of blood vessels and an erection. The veins carrying blood away from the region constrict and help keep blood present allowing the erection to persist. This phenomenon is termed vasocongestion and also occurs in the testicles. The size of the testicles can increase by 25-50% during sexual arousal. The lack of orgasm allows this congestion to persist and is felt as an ache or pain in the testicles. Hence the term "blue balls". Some describe the sensation as heaviness.
Scientists now know that a similar phenomenon occurs in women due to the vasocongestion process and produces an ache in the pelvis and lower abdomen.
Blue balls is nothing more than an uncomfortable sensation and should not result in the partner being pressured into sex. No damage will occur if the male does not ejaculate. The vasocongestion theory makes the most sense, but others in the medical community believe it has to do with the epididymis. The epididymis carries sperm and some theorize that sperm backing up in this tube results in the discomfort known as blue balls. The term blue balls relates to the bluish discoloration that may appear in the scrotum due to vasocongestion. The testicles themselves do not actually turn blue.
Most importantly, this condition is not dangerous or life threatening. If ejaculation does not occur, discomfort resolves within an hour. The following are some reliefs for blue balls.