Preputial sac

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Preputial sac is the term applied to the space on the penis between the prepuce and the glans penis.[1] The preputial sac may also be called the sub-preputial space or preputial cavity.


When boys are born, the preputial sac is sealed shut by a synechia called the balanopreputial lamina,[2] so it cannot be infected. The preputial sac will remain closed for a variable number of years.

The preputial sac is lined with mucosa as is appropriate for an internal organ where moisture is present.[3] Urine and other sources of moisture are not harmful to it.

The glans penis (head of the penis) is covered and protected from friction and abrasion by the foreskin while it is in the preputial sac, so it does not accumulate keratin, and maintains its natural sensitivity.

Parkash et al. (1973) reported that epithelial debris [exfoliated skin or mucosa] accumulates in the preputial sac and forms smegma.[4], a natural, normal, benign, healthy, and beneficial product of the body, which will collect harmlessly in the preputial sac.

Wetness in the preputial sac is normal and associated with having a longer prepuce.[5] Parkash et al. (1982) studied the wetness to learn its source. The authors concluded "that the space is kept moist and also clean in those with preputial stenosis, by the secretions of the prostate, supplemented by the seminal secretion of the mucin content of the secretion of the urethral glands."[6] The preputial sac may also receive pre-ejaculate. The authors further reported that the wetness is rich in lytic material.[6] Lytic material causes lysis or a breakdown of pathogen cell walls.[7] Moistness also may be maintained by transudation.[3] The sac may vary from very slightly moist to wet.

A longer prepuce helps to keep out contaminants and pathogens. Lakshmanan & Parkash (1980) described the muscle fibers in the prepuce (known as the dartos), which contract to keep the prepuce snugly close to the glans penis.[8] The muscle fibers form a whorl at the tip to keep the tip of the foreskin and keep the preputial sac closed against the outside world and contamination.[9]

Cold & Taylor (1999) described a healthy microbiome that lives within the preputial sac.[3] They also reported that Langerhans cells are found in the mucosa of the preputial sac. Langerhans cells are part of the immunological defenses of the penis.

De Witte et al. (2007) reported that Langerhans cells produce a substance named langerin. The langerin offers protection against HIV infection:

Langerin is a natural barrier to HIV-1 transmission by Langerhans cells
Langerin prevents HIV-1 transmission by LCs. HIV-1 captured by Langerin was internalized into Birbeck granules and degraded. Langerin inhibited LC infection and this mechanism kept LCs refractory to HIV-1 transmission; inhibition of Langerin allowed LC infection and subsequent HIV-1 transmission. Notably, LCs also inhibited T-cell infection by viral clearance through Langerin. Thus Langerin is a natural barrier to HIV-1 infection, and strategies to combat infection must enhance, preserve or, at the very least, not interfere with Langerin expression and function.[10]

The foreskin produces pheromones that are likely to be present in the preputial sac.[9]


Birley et al. (1993) studied 43 men with recurrent or persistent balanitis at an outpatient genitourinary disease clinic in London, UK where most men are intact. Of the study group only 33 percent were circumcised. Birley and colleagues discovered that the men in that group washed frequently with soap.

The men were instructed to wash less frequently, to stop using soap, and to treat with emollients. The soap and shower gel apparently removed the natural skin oil, which appears to be essential for health of the mucosa of the preputial sac.[11]

Fleiss, Hodges & Van Howe (1998) reported the presence of cathepsin B, lysosyme, chymotrypsin, neutrophil elastase, and cytokine in the sub-preputial moisture. These substances have a destructive lytic effect on pathogens and make the preputial sac a trap for disease-causing organisms.[9]

The presence of the healthy microbiome, the Langerhans cells, and the lytics in the sub-preputial moisture give the preputial sac strong immunological functions. Circumcision destroys the preputial sac and its protective immunological functions and makes the patient more vulnerable to infection throughout life.[9]

One frequently hears the advice to wash the preputial sac at least daily to prevent infection. This advice is outmoded.[11] [9] Washing may introduce pathogens into the preputial cavity.[9] It also removes the skin oil and protective lytic substances described above. It is better to rinse only as necessary, using only clear warm water.[12] It is customary to wash before and after sex.

If the foreskin is non-retractable, then a rubber-bulb ear syringe may be used to squirt warm water into the foreskin to flush it out for an occasional washing. Washing is recommended before and after sex and as desired to remove accumulated smegma.

Soap, body wash, and shampoo should not be used inside the preputial sac, because they remove the beneficial skin oil.


Intact men sometimes ask, "do I have to retract my foreskin when I pee?" They may have been heard myths that it is unhealthy to have urine inside the foreskin, however there is no factual basis for that claim. Urine is normally sterile when it leaves the urethra and is helpful for flushing out the foreskin and keeping it clean. Boys by necessity pee through their foreskin because it does not retract and men with phimosis also pee through their foreskin because the foreskin does not retract. It does no harm so it is not necessary to pull back when you pee.

Everything in the preputial sac is covered with mucosal membrane (similar to the inside of your mouth), which likes to be wet, so no damage or threat to health is caused by having urine inside the foreskin. The sphincter action of the preputial orifice functions as a one way valve, blocking the entry of contaminants and pathogens while allowing the passage of urine.[9] The urine will help to flush contaminants and pathogens out of the foreskin. Some individuals may experience ballooning of the foreskin, which is harmless.

The foreskin overhang or acroposthion may be used as a hose nozzle to control and direct the stream. It may help to stretch one's foreskin out from one's body. One man said, "When I need to pee, I open my fly, pull my foreskin out and give it a tug to get any wrinkles out, then I hold my foreskin with the thumb and forefinger of both hands and use the overhang of my foreskin to direct my stream. When I finish, I milk it a bit to get any residual pee out of my urethra."

Foreskinned men may report feeling a slight tickling sensation as the urine flows out through their acroposthion.

One may pull back or not pull back when urinating. Either way is okay.


A NSFW video of a foreskinned man urinating through his acroposthion.

See also

External links


  1. REFweb (2012). preputial sac, The Free Dictionary by Farlex. Retrieved 7 October 2022.
  2. REFjournal Deibart GA. The separation of the prepuce in the human penis. Anat Rec. 1933; 57: 387-99. DOI. Retrieved 23 May 2023.
  3. a b c REFjournal Cold CJ, Taylor JR. The prepuce. BJU Int. January 1999; 83, Suppl. 1: 34-44. PMID. DOI. Retrieved 8 July 2021.
  4. REFjournal Parkash S, Jayakumar S, Subramanyan K, Chaudhuri S. Human subpreputial collection: its nature and formation.. J. Urol.. August 1973; 110(2): 111-2. PMID. DOI. Retrieved 7 October 2022.
  5. REFjournal O'Farrell N, Chung CK, Weiss, Helen. Foreskin length in uncircumcised men is associated with subpreputial wetness. Int J STD AIDS.. December 2008; 19(23): 821-3. PMID. DOI. Retrieved 7 October 2022.
  6. a b REFjournal Parkash S, Raghuram R, Venkatesan K, Ramakrishnan S. Sub-preputial wetness - Its nature. Ann Nat Med Sci (India). July 1982; 16(3): 109-12. Retrieved 7 October 2022.
  7. REFweb (2012). Lytic, The Free Dictionary by Farlex. Retrieved 7 October 2022.
  8. REFjournal Lakshmanan S, Parkash S. Human prepuce: some aspects of structure and function. Indian J Surg. 1980; 44: 134-7.
  9. a b c d e f g REFjournal Fleiss P, Hodges F, Van Howe RS. Immunological functions of the human prepuce. Sex Trans Infect. October 1998; 74(5): 364-67. PMID. PMC. DOI. Retrieved 14 January 2022.
  10. REFjournal de Witte L, Nabatov A, Pion M, Fluitsma D, de Jong MAWP, de Gruijl T, Piguet V, van Kooyk Y, Geijtenbeek TBH. Langerin is a natural barrier to HIV-1 transmission by Langerhans cells PDF. Nature Medicine. 4 March 2007; 13(3): 367-71. PMID. PMC. DOI. Retrieved 6 October 2022.
  11. a b REFjournal Birley HDL, Walker MM, Luzzi GA, Bell R, et al. Clinical Features and management of recurrent balanitis; association with atopy and genital washing] PDF. Genitourin Med. October 1993; 69(5): 400-3. PMID. PMC. DOI. Retrieved 9 October 2022.
  12. REFbook Bigelow, Jim (1994): The Reputation of the Foreskin in America, in: The Joy of Uncircumcising!: Exploring Circumcision: History, Myths, Psychology, Restoration, Sexual Pleasure, and Human Rights. Edition: 2. Hourglass Book Pub. Pp. 74. ISBN 978-0934061223.