Epididymal hypertension or "blue balls" refers to testicular aching that occurs after extended sexual activity without orgasm. When aroused, the blood vessels in the genital area fill with blood; and if the pressure is not dissipated by achieving orgasm it can cause great discomfort. The reason the balls appear to turn blue is due to color changes in the skin of the scrotum. Oxygen rich blood on the surface of the skin creates a red color, while blood with little oxygen looks blue. The longer blood stays in the testes and scrotum without circulating to the heart and lungs the less oxygen it obtains and the more blue the skin looks.
When a man becomes sexually aroused, the arteries that carry blood to his genitals enlarge, while the veins that leave the genital area constrict, allowing less blood to escape. This uneven blood flow causes blood to be trapped in the genital area, producing an erection and making the testes swell to be 25-50% larger than their normal size. Once orgasm is achieved, the blood vessels will return to their normal size and the volume of blood in the genitals returns to its normal level rather quickly. If a man does not have an orgasm, the vasocongestion process builds up a pool of blood in the genitals leaving a sensation of heaviness, aching, or discomfort.
Epididymal hypertension usually does not last long and often the pain associated with blue balls is minor, unless there has been prolonged sexual stimulation without orgasm. Most men are also frustrated when they get an erection during sexual activity, but do not achieve orgasm. The frustration and disappointment associated with not being able to have an orgasm can add to the physical discomfort, making blue balls seem even worse. Men who feel pressure to ejaculate every time they are aroused may attempt to pressure an unwilling partner to proceed with sex.
The simplest remedy for blue balls is orgasm and ejaculation. Masturbation is the easiest way to achieve orgasm, especially if one's partner is not ready for intercourse. The pain can also dissipate slowly on its own, even without orgasm once the individual is no longer aroused. Realizing that ejaculation is not a requirement in all sexual situations can help both men and women to become more comfortable together and relax.
Women can also be affected by pelvic congestion, or blue vulva, and experience the discomfort of unreleased vasocongestion. During sexual arousal women's vulva, uterus, and ovaries swell with blood, causing the same feeling of heaviness and aching that men experience. This discomfort in women can also be relieved by having an orgasm or merely waiting for a period of time.