This article is about smegma, a secretion of mammalian genitals. See Vernix caseosa for the substance that covers the skin of a baby at birth. See Smegma (band) for the experimental noise band.

Smegma, from the Greek smēchein (to clean)¹, is a combination of exfoliated (shed) epithelial cells, transudated skin oils, and moisture. In males, smegma helps keep the glans moist and facilitates sexual intercourse by acting as a lubricant.²³⁴

Human smegma

Both males and females produce smegma. In males, smegma is produced and accumulates under the foreskin; in females, it collects around the clitoris and in the folds of the labia minora.

Males

Smegma on a penis

Smegma was originally thought to be produced by sebaceous glands near the frenulum called Tyson's glands, however subsequent studies have failed to find these glands.⁵ Wright states that smegma is produced from minute microscopic protrusions of the mucosal surface of the foreskin and that living cells constantly grow towards the surface, undergo fatty degeneration, separate off, and form smegma.² Parkash et al. found that smegma contains 26.6% fats and 13.3% proteins, which they judged to be consistent with necrotic epithelial debris.⁵ Newly produced smegma has a smooth, moist texture. It is thought to be rich in squalene⁶ and contain prostatic and seminal secretions, desquamated epithelial cells, and the mucin content of the urethral glands of Littré.⁴ Some state that it contains anti-bacterial enzymes such as lysozyme and hormones such as androsterone,⁴³ others dispute this.⁷

According to Wright, little smegma is produced during childhood, although the foreskin may contain sebaceous glands. She also says that production of smegma increases from adolescence until sexual maturity when the function of smegma for lubrication assumes its full value, and from middle-age production starts to decline and in old age virtually no smegma is produced.² Oster reported that the incidence of smegma increased from 1% among 6-7 year olds to 8% among 16-17 year olds (an overall incidence of 5%).⁸

One study indicated that infrequent washing may allow colonization of the preputal space by pathogenic bacteria.⁹ Another study found that subjects who retracted the foreskin when bathing were less likely to have smegma accumulation, inflammation, phimosis, or adhesions than those who did not.¹⁰

An early study by Plaut and Kohn-Speyer (1947)¹¹ found that horse smegma had a carcinogenic effect on mice. Heins et al.(1958)¹² used human smegma on mice and found a carcinogenic effect, but Reddy and Baruah (1963) were unable to reproduce this effect, concluding that if a carcinogenic effect did exist, it must be weak. In other more recent studies, smegma was found to be a risk factor among penile cancer patients.¹³¹⁴ However, the American Cancer Society says that smegma itself is probably not carcinogenic,¹⁵ and a recent review concluded that "the evidence does not support the theory that smegma is a cause of genital cancer."³

Females

Glands that are located around the clitoris and the vulva secrete sebum. The accumulation of sebum combined with dead skin cells forms smegma.

In both sexes, preventing accumulation is best done by rinsing the area with warm water. In females, the hood of the clitoris can be gently pulled back to wash away accumulated smegma. Some argue that soap is best avoided because it depletes natural skin oils and may cause non-specific dermatitis.¹⁶

Non-human smegma

In healthy animals, smegma helps clean and lubricate the genitals. In veterinary medicine, analysis of this smegma is sometimes used for detection of urogenital tract pathogens, such as Tritrichomonas foetus.¹⁷ Accumulation of smegma in the equine preputial folds and the urethral fossa and urethral diverticulum can promote the carriage of Taylorella equigenitalis, the causative agent of contagious equine metritis.¹⁸ Some veterinarians have recommended periodic cleaning of male genitals to improve the health of the animal.¹⁹

References

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Smegma