This is the most common perianal dermatosis seen by dermatologists. It presents with perianal pruritus, which may be severe and occasionally painful. Sleep disturbance is common [1, 2]. Perianal dermatitis may be exacerbated by fecal leakage [1–3]. Patients may have a history of atopic dermatitis or contact dermatitis [4]. Clinical examination often reveals a diffuse erythema of the perianal skin with lichenification and often excoriations.

Internal hemorrhoids can exacerbate perianal dermatitis, but perianal pruritus has rarely been reported in conjunction with rectal polyps and carcinoma [5]. It is therefore recommended that all patients have a sigmoidoscopy, that internal hemorrhoids be appropriately treated, and any concurrent rectal pathology be reviewed.

All patients should be educated about appropriate hygiene. Most patients overclean the area with soaps, baby wipes, and/or excessive water. Soaps are an irritant that may exacerbate pruritus and inflammation. Patients with perianal dermatitis are at high risk for contact dermatitis from ingredients in soap, such as fragrances [4]. Wet wipes often contain preservatives such as methylisothiazolinone, which are potent contact sensitizers [4] and should be avoided. Patients should be advised to clean the area once daily with only water and to dab the area dry avoiding excessive friction.

There is no evidence that dietary measures improve perianal dermatitis. Although it has been postulated that caffeine can reduce anal tone and perhaps increase anal leakage [7], there is no evidence that avoiding caffeine improves symptoms. This lack of evidence also applies to avoiding spicy foods, alcohol, and any other dietary manipulation. Given this lack of evidence, there seems to be little logic in recommending such interventions. Topical anesthetic preparations such as lidocaine or cinchocaine are ineffective for pruritus and should be avoided because there is a significant risk for contact sensitization [8].

There is evidence that chronic pruritus can result in reduced anal sphincter tone with microscopic leakage of fecal material after defecation [3]. Feces are highly irritant to the skin and may exacerbate skin that is already inflamed. The use of a barrier cream such as zinc oxide after a bowel movement may prevent fecal material from irritating the perianal skin. Mild-potency topical steroids such as 1 % hydrocortisone ointment may be effective, especially when applied at night before sleep. One percent hydrocortisone does not cause skin thinning, unlike more potent topical steroids.

It is recommended that all patients undergo contact allergy testing or patch testing. Up to 30 % of patients with perianal dermatitis have a relevant contact allergy [9]. Patients should be tested for several allergen series according to local protocols. In our centre, patients are tested to the British standard series, the fragrance series, the medicament series, the textile series, and their own leave-on products. The patches are applied on the back on Monday and read on Wednesday and Friday of the same week. Patch testing should only be done by medical and nursing staff who have appropriate training [4]. The most common allergens in patients with perianal dermatitis are fragrances, preservatives such as methylisothiazolinone [6], and sodium metabisulfite [10], which are used in wet wipes and medicaments such as cinchocaine [2, 8]. Contact allergens may include nail varnish [11], topical steroids [4], and textile dyes [12]. The majority of patients who are investigated and treated according to the above protocol achieve remission of their pruritus. Patients with more refractory disease may require more potent topical steroids, topical tacrolimus, and/or systemic antipruritic therapies.