The Sex Series – Part Seven: Mast cell activation and anal penetration

So far in this series, we have talked a lot about vaginally penetrating sex.  But that’s not the only way to have sex so for now, let’s move on.

Anally penetrating sex can be safe, painless and pleasurable for many people.  It is enjoyed by many partners of various sexual orientations.  The anus is an inherently different environment than the vagina and as such, preparation for and participation in anally penetrating sex is a bit different.

An obvious difference is that the anus does not self-lubricate in preparation for sex.  Use of external lubricant is HUGELY important.  Silicone based lubes are often used for anally penetrating sex because it is slicker and is not broken down as quickly by your body as water based lubricants. When selecting a lubricant, be sure to research whether components can irritate the anus and rectum.  In particular, many spermicides are very irritating to rectal tissue. Of course, in the same way that a person can react to lubricant in the vagina, you can react to lubricant in the rectum and anus.  Contact dermatitis or other types of allergic reaction can occur.

Though “vigorous anal penetration” is often considered a risk factor for anal or rectal injury, the actual incidence of these injuries is low and mostly occurs in sexual assault situations.  Injury to the sphincter musculature is unusual.  Large patient groups of gay men who engage in anal sex have been surveyed regarding issues or injuries associated with receiving anal penetration over a long period of time.  Some patients reported infrequent or “slight” incontinence, attributed by medical professionals to the inability of the anal sphincter to close as tightly in the immediate time after penetration.  However, in other studies, no patients have reported this issue.  The most frequent problem, as also seen in vaginal intercourse, is the transmission of sexually transmitted infections.  This can be mitigated by using condoms.

Anal penetration should not hurt.  The person receiving and giving should take steps to relax the anal sphincter, use adequate lubrication, and be sensitive to any pain.  Painful penetration can indicate a problem and should be taken seriously by both partners. Regardless of how an injury was acquired, anal sex can irritate any condition that affects the rectum or anus.

Hemorrhoids are blood vessels that become distended.  They can occur internally or externally, and are often painless.  The first indication of hemorrhoid is often bright red blood on toilet paper.  If a blood clot forms in the hemorrhoid, it can become very painful and swollen.  It is not entirely understood how hemorrhoids form, but straining to stool, increased pressure in the abdominal cavity, obesity and pelvic floor dysfunction are often linked to formation.

Mast cells are increased in hemorrhoid associated tissue and may affect hemorrhoid formation and resolution through release of mediators like tryptase, chymase and platelet activating factor. One study found that the number of mast cells in acute and chronic hemorrhoids is not different, indicating that mast cells can be associated throughout the lifecycle.

Fissures are tears in the anal or rectal tissue.  Fissures can be very painful, especially during and after defecation.  Fissures also cause bright red blood on the toilet paper or stool.  Patients who have fissures often have increased resting pressure when tested with anorectal manometry, meaning their muscles are more tense than usual.  Fissures can also be mast cell activating, as mast cells are active in wound healing.  Tears in the rectum and anus do not heal as quickly as those in the vagina.

Rectal itching is not unusual in allergy/mast cell patients.  Mast cells are natively present in the rectum and can degranulate in response to stimuli just like mast cells anywhere else.  Mediators released can also cause pain.  Care should be taken to reduce friction as much as possible to try to prevent degranulation from pressure.  Itching and pain can also be signs of reacting to condoms or lubricants used.

Pelvic floor dysfunction can also make anal sex painful, as the rectum and anus may not be properly supported by connective tissue.  Patients with pelvic floor dysfunction or connective tissue defects should be cautious to observe any pain or discomfort when receiving anal penetration. Pelvic floor dysfunction, and the other conditions mentioned above, can be irritated by anal penetration.

As described earlier in the series, it is possible to have an allergic reaction to semen, either due to the presence of allergens or to the composition of the semen itself. If semen enters the body during anally penetrating sex, it is possible to have an allergic reaction.  Condoms can prevent these reactions, and are also recommended to decrease risk of infection due to contact with GI flora.



Chond PS, Bartolo DCC. Hemorrhoids and fissure in ano. Gastroenterol Clin N Am 2008, 37: 627-644.

Cawich SO, et al. Complete anal sphincter complex disruption from intercourse: A case report and literature review. International Journal of Surgery Case Reports 2012: 3, 565-568.

Zamvar V, et al. Severe anal pain caused by food allergy?: A case report. European e-Journal of Clinical Nutrition and Metabolism 2010, 5: e144-e145.

Taweevisit M, et al. Increased mast cell density in haemorrhoid venous blood vessels suggests a role in pathogenesis. Singapore Med J 2008; 49 (12): 977-979.