Keywords

Nomenclature and Definitions

The word smegma is from Greek “smēgma” meaning soap or an ointment. It produced in both male and female mammalian genitalia; in males smegma accumulated commonly under the foreskin and in female it is collected around the clitoris and in the folds of the labia minora. Also smegma can be found in other genital intertrigo. It is just a genital form of body sebum. Its production increases in puberty and remains high in adults to decline in old age.

Historical Background

French physician, Claude-François Lallemand (1790–1853), pronounced that smegma could provoke erections that would lead to ‘disastrous pleasures’.

American physician Roberts Bartholow (1831–1904) formulated the theory that smegma produced ‘hyperæsthesia’ of the glans.

American urologist Abraham Wolbarst (1872–1952), who updated the demonization of the foreskin and promulgated the idea that it harboured ‘carcinogenic secretions’.

Smegma was originally thought to be produced by sebaceous glands near the frenulum called Tyson’s glands. The English Anatomist Edward Tyson (1650–1708) described a modified sebaceous glands in the coronal sulcus, which he stated were responsible for smegma production. He never published his observations, but he noted them in a syllabus that was distributed to his students. Tyson inserted the words ‘Glandula Mucilaginosa’ under the heading ‘Urethra Ejus’ with a footnote stating that he had discovered such glands [1]. A modern interpretation indicated that his observations might have been in reference to primates rather than humans. Tyson might have described the condition that is at the present known as papillomatosis corona penis (Pearly penile papules), which is not related to sebaceous glands [2, 3].

Composition

Wright [4] 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. 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.

The smegma is cheese-like sebaceous matter is a combination of shed skin cells, skin oils, and moisture. A natural secretion of skin cells and oils that collects under the foreskin in both males and females. If allowed to grow stale, it may have a pungent aroma (commonly compared to cheese in males or fish in females) [1].

Newly produced smegma has a smooth, moist texture. It is thought to be rich in squalene [5].

The presence of fructose and acid phosphatase in subpreputial material and the absence of urea, leads Prakash S and Jeyakumar [6] to indicates the presence of seminal vesical and prostatic secretions in smegma, they also reported that smegma is a subpreputial collection of desquamated epithelial debris, mixed with mucin, and secretions with a composition including fat (about 27%) and protein (about 13%), which consistent with necrotic epithelial debris.

Others claim that smegma contains prostatic and seminal secretions, desquamated epithelial cells, and the mucin content of the urethral glands of Littré [7].

Those who claim an immunological function of smegma reported finding of chymotrypsin, neutrophil elastase, cytokines cathepsin B, and lysozymes, which aid the immune system [8, 9].

Bacteriology

There are few studies investigating the colonisation and exact nature of smegma that had never been exposed to the outside in the subpreputial space between the inner prepuce skin and glans surface before prepuce excoriate. In one study smegma is found to be sterile [10].

In a study from Nigeria, they founded bacterial isolates in smegma swabs from 52 boys ranging in age from 7 days to 11 years. A single isolate was found in 34 boys (65.4%), eight had a mixed isolate (15.4%), while no bacteria was isolated in 10 boys (19.2%). The commonly isolated gram-positive bacteria were Staphylococcus epidermidis (44.8%) and S. aureus (41.4%) and the most commonly isolated gram-negative bacterium was E. coli (90.5%). Most of the bacterial isolates were multi-drug resistant. They suggested the differences in the organisms from other studies, means a local variation due to differences in climate and diet, but also the socio-economic differences in the various populations [11].

Some authors in order to prove the role of smegma in induction of UTI, they claimed that virgin smegma in the subpreputial space of children was colonized by many kinds of uropathogen of E. coli, which may predispose to UTI and leads to increased its high prevalence in uncircumcised boys [10].

Functions

Smegma beneficially serves to preserve subpreputial wetness. The main function of smegma is moisturising and lubricating the cavity between the foreskin and the glans that is the subpreputial space, facilitating erection, preputial eversion and penetration during sexual intercourse. This natural lubricant allows for prolonged intercourse and eliminates the need for artificial supplemental lubrication during normal coitus or masturbation [12].

Smegma had a pheromonal (sexual attractant), this is obvious in certain animals, but it is uncertain in human and perhaps it had bacteriostatic functions. The power of an accumulation of smegma to erogenously stimulate the nervous system was consistent with the accepted theory of reflex ‘irritation’, a term then understood to mean ‘stimulation’ rather than its modern connotation of discomfort [1].

It may contain anti-bacterial enzymes including lysozyme and hormones like androsterone, although this is equivocal [13].

It also may contain immunologically active chemical compounds such as cathepsin B, lysozyme, chymotrypsin, neutrophil elastase, cytokines, specially lysozyme, which probably originates from the prostate and seminal vesicles, to destroy bacterial cell walls and inhibit and destroy some candidal species [13].

Hazards

When the foreskin is not retractable smegma can accumulate between the inner surface of the foreskin and the glans and looks like a yellowish-white, clearly defined, soft mass (Fig. 17.1). During retraction of the foreskin without forcing, this mass becomes evident and sometimes protrudes over the free edge of the foreskin (Fig. 17.2).

Fig. 17.1
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Clumps of smegma aggregation under a nonretractable prepuce

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Fig. 17.2
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Protruded smegma mass after managing the prepuce to retract

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Smegma may aggregates to form a lump or it may become hard to form a smegma stone or smegmoliths, smegma may be entrapped between the edges of the circumcision wound to form a different shapes and sizes of smegma cysts (Fig. 17.3).

Fig. 17.3
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Small smegma cyst formed between the edges of circumcision wound

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Smegma cysts of different sizes may be also formed in the circumcised penis distal to the edges of the wound, this may be due entrapment of smegma particles between penile or preputial skin layers (Fig. 17.4).

Fig. 17.4
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Entrapped smegma cysts under the preputial remnants

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Smegma accumulations may induce irritation with a subsequent dermatitis (balanitis or balanoposthitis), also aggregated smegma may be colonised with different pathogenic bacteria and became a source of infection.

Circumcision will not abolish smegma secretion, but it will reduce the chance of its accumulations, circumcised boy may still accumulates smegma, if it is not cleaned and washed frequently.

Figure 17.5 showing a normally produced smegma in a circumcised boy, we can also notice the adjacent inflammation in the preputial remnant. Someone may argue that this because the circumcision is incomplete and the preputial remnant is predisposing for such complication, but in Fig. 17.6 an infant with excessive preputial removal, without any remnant, but he still had a liner smegma accumulated at the coronal sulcus. A smegma produced in circumcised boys in the same way as in uncircumcised one (Fig. 17.7).

Fig. 17.5
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A Circumcised boy with smegma at the coronal sulcus and minimal posthitis in the preputial remnant

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Fig. 17.6
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Over circumcised infant with a smegma at the coronal sulcus

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Fig. 17.7
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Smegma produced by a circumcised boys in a same configuration as it is produced in uncircumcised one

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Smegmoliths : (Fig. 17.8).

Fig. 17.8
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A small smegmolith

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It is a concretions of smegma in the preputial sac, consisted of smegma with uric acid, and to a lesser extent calcium phosphate. It is seen with a different consistency and sizes, of greyish-yellow or tawny color, of roundish shape or oval, and consist of all or only some of those elements which make up the smegma and arranged in the form of concentric layers.

Majocchi [14], reported several cases of smegmoliths in male boys and he reffered that smegmoliths are also founded in the preputial sac of horses. He believed that B. coli acting upon urea makes ammonia which combines with the fat in the smegma and forms ammonia soaps. Urinary salts and epithelial debris are deposited around this nucleus which increases the size and the density of the smegma stones [15].

Smegma cysts discussed in Chap. 25.

When Smegma Starts to Form?

Smegma is a natural emollient secretion of skin cells and oils that collects under the foreskin in both males and females, it is firstly seen in the enlarged posterior extremity of the glandar lamella, (the future coronal sulcus in adult), approximately at sixth month of foetal life. Prepuce completely covering and fusing with the glans structure at around 24th week of gestation.

Smegma like the earwax and vernix caseosa, also known as vernix, which is the waxy or cheese-like white substance found coating the skin of newborn human babies. It is produced by dedicated cells and is thought to have some protective roles during fetal development and for a few hours after birth. There is a great similarity between smegma and vernix in texture and physical characters (Fig. 17.9).

Fig. 17.9
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Vernix caseosa at the back of a just born baby, it is physically similar to smegma. A public domain photo from Wikipedia, the file licensed under the Creative Commons Attribution-Share Alike 4.0 International license

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Smegma had no relation to the glandopreputial membrane and it is not formed by the shaded or desquamated cells of this membrane, as smegma formed and become detectable as early as the prepuce formed, and before any separations of the glandopreputial membrane, what was reported in some studies about desquamated cell detected histologically with smegma are just cells in the scene from which the smegma samples collected [7].

Researchers at Botkin’s Hospital in Moscow have asserted that smegma is produced from minute microscopic protrusions of the mucosal surface of the foreskin. According to those scientists, living cells constantly grow towards the surface, undergo fatty degeneration, separate off, and form smegma [1].

Smegma quantities and aggregations are so variable between individuals; Cowper stated that sebaceous glands producing smegma were more numerous and larger in the individuals who have a larger prepuce [16].

Many neonates delivered with an obvious smegma, or even a different forms of preputial aggregations (Fig. 17.10).

Fig. 17.10
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A neonate with a small smegma particles emerging from the preputial ring

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Smegma may be scanty, or bulky, very rarely to be absent or deficient, it is commonly arranged in row or streaks at the coronal sulcus (Fig. 17.11), rarely it may be visible at the preputial ring, or adherent to the glandular surface in a radial form (Figs. 17.12 and 17.13).

Fig. 17.11
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Smegma commonly distributed as a streaks at the coronal sulcus

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Fig. 17.12
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Plenty of smegma at the base of inner prepuce

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Fig. 17.13
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Rare distribution of the smegma as a liner streaks arranged radially over the glans

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Øster [17] reported that the incidence of absent smegma increased from 1% among 6- to 7-year-olds and 8- to 9-year-olds to 9% among 14- to 15-year-olds and 16- to 17-year-olds (an overall incidence of 5%).

In one survey, out of 18 self-selected intact men never saw smegma; 1 saw it after a week unwashed, 6 after 2 days, 8 after 1 day, and 1 after less than a day [16].

Smegma is mainly confined to the preputial sac, but it is also produced at any genital intertrigo, this gives us a strong believe that smegma is just a modified sebum secreted from the sebaceous glands of the genital area in both male and female, not only at the coronal sulcus or the preputial sac, but also from any skin crease in the genital area (intertrigo).

It is mentioned earlier by Cowper who stated that specialised sebaceous glands were located mainly at the coronal sulcus where the preputial mucosa reflected to form the inner prepuce [16].

So it is reasoning to have another similar glands producing the same smegma in other genital skin creases.

In Fig. 17.14 a neonate female with a prominent sebaceous gland and scattered area of smegma at the labia majora, this is also obvious in an older girl with a smegma not only confined to the clitoris and preputial area, but also all around the introits (Fig. 17.15).

Fig. 17.14
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A neonate girl with a prominent yellow papules and ectopic smegma scattered in the labia major

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Fig. 17.15
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An infant girl with smegma around the whole introits

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In normal children, who had a skin crease at the root of the penis, a different aggregation of smegma can be appreciated at these creases (Figs. 17.16 and 17.17). Many cases of hypospadias also may have smegma at the penile root (Fig. 17.18).

Fig. 17.16
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Smegma in a skin crease at the root of the penis

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Fig. 17.17
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Three months old boy with many smegma secreted at the root of the penis

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Fig. 17.18
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A case of hypospadias with smegma at the root of the penis

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An explicit example for the presence of smegma in an ectopic area is the case in Fig. 17.19, a young girl with an adrenogenital hyperplasia with a prominent clitoris, and she had an extensive smegma at the furrows between the phallus and labia. This a clear prove that smegma is not a preputial secretion and of course it could not be eliminated with circumcision (Fig. 17.19).

Fig. 17.19
figure 19

An interesting case of a girl with adrenogenital hyperplasia, and extensive smegma at the furrows between the enlarged clitoris and labia

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Conclusion

Few years earlier I published my concept about smegma and its distribution in my illustrative textbook of the congenital anomalies of the penis [18], and herein I could refine this concept in few points:

  • Smegma is secreted during the late intrauterine period, as many neonates, and even a preterm babies may had an accumulated smegma in their first day of life.

  • Smegma is a secretion of a modified sebaceous gland, which are mainly located at the coronal sulcus, but any intertrigo in the genital area may also produce smegma in both male and female.

  • Smegma is the natural secretion of the prepuce, like other body secretions, (like ear wax). So it is not harmful by itself, unless it is contaminated with other pathogens; either bacterial colonisation, virus overgrowth or combined organisms, or associated with phimosis.

  • Circumcision will not stop smegma production or ameliorate its effect, if any, circumcision will just help in exposing smegma for regular wash. Smegma will continue to produce and even it may accumulates in circumcised boys if not cared.

  • Smegma secretion and distribution had a great variations between individuals, without a clear explanation.

  • Some boys may present with one or more yellowish lumps on the penis that are often diagnosed by the general practitioner as a sebaceous cysts or lipoma of the penile shaft, but on assessment, these prove to be collections of retained smegma trapped by the surrounding preputial adhesions.

  • During circumcision and other penile surgery, smegma should be cleaned and removed meticulously with a saline wash, otherwise any retained small pieces will accumulate between the edges of perpetual remnants and results in different forms of smegma cyst, which may acquire a larger size and be troublesome.