The sense of itch is elicited when there is irritation on the surface of the skin like that of an insect crawling on it. It is closely associated with a tickle and its purpose is to make a person act against the offending agent by scratching or rubbing it off. In this manner, itching is a protective mechanism that is intended to warn a person of a potential danger on the skin surface and therefore to act against it as soon as possible. This sensation is elicited when highly-sensitive mechanoreceptors (itch receptors) on the skin surface are stimulated and nerve impulses travel along small unmyelinated nerve fibers to the central nervous system. It is also closely associated with and may precede the sensation of pain.
Itching, like pain, may be present in certain diseased states even without any offending agent on the skin surface. It is important to note that the itching sensation does not occur within the internal organs as these structures lack the specific itch receptors. Pain receptors, however, are present both on surface and internal structures and organs. These sensations may be triggered by mechanical or chemical injury and inflammation of the area.
What is pruritus ani?
Pruritus ani is the medical term for anal itching. The anus is the opening of the rectum that allows feces to be passed out into the environment during defecation. It is a short canal (anal canal) which is protected by the muscle and fat of the buttock. The rectum, like all other internal organs, does not have itch receptors and therefore any itching which is perceived in the area arise from the skin around the anus (perianal area). It can sometimes feel like a ‘deep itch’ leading to the misconception that it is emanating from higher up in the rectum.
Anal itching is not always indicative of bowel disorder. Often it is irritation of the skin that is unrelated to bowel health that causes anal itching. The skin of the anus is essentially same in structure as the rest of skin on the body albeit a little thinner and therefore delicate. Itching may be accompanied by a burning sensation (burning anus) or pain, both of which are an indication of inflammation of underlying tissue.
Causes of Anal Itching
Most cases of anal itching are due to unknown causes (idiopathic) and is short lived. It may resolves as quickly as it starts and every person experiences anal itching at some point in life even without any underlying disorders. Scratching can often cause further irritation and exacerbate the itching.
The other important and equally common factor is hygiene around the anus (perianal area) and personal hygiene as a whole. Insufficient cleansing of the perianal area may lead to fecal matter and bacteria remaining in the area. The feces causes irritation of the skin locally and the bacteria may lead to a skin infection particularly in view of the fact that the anus is in a warm and often moist environment between the buttocks.
Conversely, excessive cleansing of the perianal area can be as much a cause of anal itching. Overzealous cleaning can damage the delicate skin of the perianal area, while soaps and disinfectants can cause contact dermatitis. The skin maintains its health by balancing a number of factors that are responsible for maintaining a disease-free microenvironment and excessive cleansing can disrupt this thereby leading to itching.
Itching is often associated with conditions like external hemorrhoids. This is a swelling and engorgement of the rectal veins associated with a number of conditions including constipation, diarrhea, pregnancy, excessive straining during defecation and obesity. External hemorrhoids, particularly if it is large, may affect proper wiping and cleansing of the area thereby further contributing to itching as discussed above under hygiene.
Other anorectal conditions that may also be responsible include :
- Anal fissures
Skin diseases involving the perianal area may be associated with infection (discussed below) or non-infectious inflammatory conditions. The latter is seen with skin diseases such as :
- Atopic dermatitis
- Scabies (infection)
- Skin cancer
- Skin tags
Infectious causes may involve the bowels or skin. This includes :
- Intestinal parasites (parasitic worms)
- Bacterial infections of the skin
- Fungal infections particularly involving yeasts like Candida albicans
- Sexually transmitted infections as a result of anal intercourse
- Soaps, particularly strongly-scented and/or antibacterial (containing disinfectants)
- Sanitary wipes
- Latex and lubricants (intercourse)
- Local anesthetics
Foods and Drugs
Certain foods may cause pruritis ani either due to immune-mediated hypersensitivity, other mechanisms or for unknown reasons. These trigger foods may vary from person to person but more often includes :
- Hot chilli/pepper
Anal itching may arise as a side effect of certain drugs, at times without a clearly understood cause, while at other times it is a result of diarrhea associated with drug use. Antibiotics are one of the drugs that may be associated with anal itching.
Treatment of Pruritus Ani
Treatment has to be directed at the cause.
- Antihistamines may provide symptomatic relief and be of use in the long term management of allergy-related conditions.
- Corticosteroids may be used in chronic inflammatory conditions.
- Antimicrobial agents are necessary for infections.
- Diarrhea and constipation need to treated accordingly and patients with frequent bowel movements may benefit from probiotics.
Remedies for Anal Itching
Conservative measures should always focus first on hygiene. Proper but not excessive cleansing is essential. Patients need to be aware of the itch-scratch-itch cycle where scratching the itchy anus may further exacerbate the itching and cause excoriation of the skin in the perianal area. Sometimes the best remedy for the odd episode of anal itching is to “do nothing”.
- Wipe the area thoroughly after defecation with soft, hypoallergenic toilet paper and use water if necessary. Excessive wiping should be avoided.
- Do not delay while sitting on the toilet during defecation.
- Avoid rubbing the perianal area excessively when bathing and do not use any coarse material to scrub the area as the skin is delicate.
- Identify any trigger foods and avoid it as far as possible.
- Patients with irritable bowel syndrome (IBS) should avoid sitting on the toilet with every urge unless defecation is necessary.
- Use light, airy clothing and avoid tight underwear particularly those garments that make direct contact with the perianal area.
- Excessive sweating may also cause anal itching and patients with hyperhidrosis should take extra measures like using non-scented drying powders in these areas.