This is the sensation of persistent perianal itching, resulting in a desire to scratch the anus. It is a symptom and NOT a diagnosis.
- Pruritus ani is present in 1-5% of the population.
- It is four times more common in men than in women.
- It can occur at any time of life but is more common between 40-60 years of age.
Nearly 100 causes have been reported for pruritus ani.
Idiopathic or primary pruritus ani
This is thought to be either functional or psychological in nature:
- Functional: due to very slight faecal matter around the anus causing irritation.
- Psychological: complex aetiology.
Secondary pruritus ani
Causes of secondary pruritus ani are numerous and include:
Thought to account for 50% of secondary pruritus ani.
- Contact dermatitis
- Atopic dermatitis
- Skin tags
- Lichen sclerosus
- Lichen planus
- Seborrheic dermatitis
- Hidradenitis suppurativa
- Bowen's disease
- Paget's disease
- Fungal - candida, dermatophytes.
- Parasitic - threadworms or scabies. Threadworms are the most common cause in children.
- Viral - condyloma secondary to human papillomavirus, herpes simplex.
- Sexually transmitted infections - gonorrhoea, syphilis. Consider if history of anal intercourse.
Rectal and anal pathology
- Anal or colorectal cancer - accounts for 23% of anal causes.
- Haemorrhoids - accounts for 20% of anal causes.
- Anal fissure - accounts for 12% of anal causes.
- Anal fistula.
- Faecal incontinence or faecal soiling.
- Chronic diarrhoea or constipation.
- Diabetes mellitus
- Aplastic anaemia
- Iron-deficiency anaemia
- Thyroid disorders
- Liver disease
- Peppermint oil.
- Antibiotics such as metronidazole or tetracycline.
- Topical preparations.
- Chilli peppers
- Duration and pattern of itch. Itch due to threadworms occurs mainly at night. If all family members are affected consider scabies.
- Triggers and irritants. Establish whether it is affected by certain foods, clothes or topical preparations. Ask about the use of powders, creams and soaps.
- Hygiene. Establish whether there is any difficulty in keeping the area clean or dry.
- Associated symptoms. May give clues as to the cause - eg:
- Pain - fissure.
- Discharge - infection.
- Bleeding - more likely to have anal pathology such as haemorrhoids, tumour, fissure.
- Change in bowel habit - consider malignancy.
- Past medical, allergy and medication history - to include causes in section above.
- Severity and impact on life.
- Look for dermatological conditions elsewhere.
- If symptoms suggest, perform a general examination to exclude other systemic disease.
- External examination of the area around the anus may reveal a cause such as a skin condition, threadworms, fissure.
- The appearance will depend upon the severity and duration of the pruritus.
There may be:
- Erythema or inflammation.
- Excoriation and cracking.
- A shiny appearance to the anal ring in chronic cases.
- Perform a digital rectal examination (DRE) if there is any suspicion of malignancy. Also consider DRE if there are internal haemorrhoids or in those with constipation.
- Do not perform a DRE in children.
Treat secondary causes.
- Avoidance of scratching. Keep nails short and wear cotton gloves at night if need be.
- Avoidance of irritants around the anus, such as scented soaps, talcum powder, bubble bath, perfume, etc.
- Good personal hygiene. Washing the anus after opening bowels and before bedtime. Drying the area by gentle patting with a towel.
- That excessive moisture around the anus can contribute to the problem, particularly if the patient is obese and/or hairy. A hairdryer may be useful for thoroughly drying the area after washing. A cotton tissue placed in the underwear may help to absorb extra moisture throughout the day. Cotton underwear should be used in preference to synthetics. Tights and tight clothing should be avoided.
- Dietary modification may be useful if implicated in causation. Trying avoidance of known potential dietary triggers (see above) and following a diet which keeps stools well formed to avoid potential soiling may be beneficial.
Symptomatic treatment options
Consider treatment options which aim to break into the itch-scratch cycle:
- Soothing ointments such as bismuth subgallate or zinc oxide for excoriated skin.
- Mild topical corticosteroids for inflamed skin (maximum 14 days to avoid the risk of atrophy and contact dermatitis).
- Capsaicin 0.006% cream has been used with debatable success in some trials.[4, 5]
- Sedative antihistamine at night time to aid sleep.
Consider referral to a colorectal surgeon or dermatologist in anyone who has had no relief after 3-4 weeks of conservative measures. Referral would also be required for those in whom a secondary cause has been discovered which needs secondary care management.
Unless a cause is found it may become a chronic complaint. Most people respond well to simple measures but may have periodic relapse.
Further reading and references
Pruritus ani; DermNet NZ
Song SG, Kim SH; Pruritus ani. J Korean Soc Coloproctol. 2011 Apr27(2):54-7. Epub 2011 Apr 30.
Pruritus ani; NICE CKS, September 2012 (UK access only)
Siddiqi S, Vijay V, Ward M, et al; Pruritus ani. Ann R Coll Surg Engl. 2008 Sep90(6):457-63.
Fargo MV, Latimer KM; Evaluation and management of common anorectal conditions. Am Fam Physician. 2012 Mar 1585(6):624-30.
MacLean J, Russell D; Pruritus ani. Aust Fam Physician. 2010 Jun39(6):366-70.
Gooding SM, Canter PH, Coelho HF, et al; Systematic review of topical capsaicin in the treatment of pruritus. Int J Dermatol. 2010 Aug49(8):858-65. doi: 10.1111/j.1365-4632.2010.04537.x.
Samalavicius NE, Poskus T, Gupta RK, et al; Long-term results of single intradermal 1 % methylene blue injection for Tech Coloproctol. 2012 Jun 6.