Pruritis ani

This is intractable itching around the anus. Usually the skin is reddened hyperkeratotic and may become cracked and moist. The causes are numerous. A useful mnemonic is: ‘pus, polypus, parasites, piles, psyche’.

Lack of cleanliness, excessive sweating, and wearing rough or woollen underclothing are common causes.

An anal or perianal discharge which renders the anus moist. The causative lesions include an anal fissure, fistula in ano, prolapsed internal or external haemorrhoids, genital warts and excessive inges­tion of liquid paraffin. A mucous discharge is an intense pruritic agent and a polyp can be the cause.

A vaginal discharge, especially due to the Trichomonas vaginalis.

Parasitic causes. Threadworms should be excluded, especially in young subjects. Children suffering from threadworms should wear gloves at night, less they scratch the perianal region and are reinfested with ova by nail biting — ‘parasites lost, parasites regained’. Scabies and pediculosis pubis may infest the anal region.

  Epidermophytosis is a common cause especially if the skin between the toes is also infected. Microscopic and cultural examinations are essential. Half-strength Whitfield’s ointment quickly gives relief and is the sheet anchor of treatment.

Allergy is sometimes the cause, in which case there is likely to be a history of other allergic manifestations, such as urticaria, asthma or hay fever. Antibiotic therapy may be the precipitating factor.

Skin diseases localised to the perianal skin — psoriasis, lichen planus and contact dermatitis.

Bacterial infection. Intertrigo due to a mixed bacterial infection. Erythrasma due to Corynebacterium minutissimum is responsible for some cases and its presence is detected by ultraviolet light which induces a pink fluorescence.

A psychoneurosis. It is alleged that in a few instances neurotic indi­viduals become so immersed in their complaint that a pain—pleasure complex develops, the pleasure being the scratching. Possibly this is true, but such a syndrome should not be assumed without firm grounds for coming to this conclusion.

Diabetes. Diabetes can sometimes present with pruritus ani and the urine should be tested in all patients.

Treatment. The cause is treated. Other methods include the following.

Hygienic measures. Cotton wool should be substituted for toilet paper. Soap is avoided and replaced by a detergent. These measures alone, combined with wearing cotton cellular underwear and appli­cations of calamine lotion, are all that is necessary to cure some cases. If there is much anal hair trapping the moisture and discharge, shaving can be very helpful.

  Hydrocortisone. In cases with dermatitis, and only in cases with dermatitis, prednisolone, applied topically in a cream of 1 per cent is often beneficial; sometimes after discontinuation of the therapy, the pruritus is liable to return, in which event 5 per cent xylocaine ointment can be substituted for a time.

Strapping the buttocks apart is a most useful procedure, especially when the pruritus is acute, and in chronic cases when the opposing surfaces are moist. The strapping is worn so long as the patient finds it beneficial.

Operative treatment

This may be necessary for a concomitant lesion of the anorectum which is thought to initiate or contribute to the pruritis. Otherwise, surgery is not indicated.