Intradermal injection of methylene blue for the treatment of refractory pruritus ani

Idiopathic pruritus ani is a common perianal condition that can be refractory to diligent perineal care. We wished to evaluate the efficacy and side effects of intradermal methylene blue for the treatment of refractory pruritus ani. A prospective series of 49 patients with idiopathic pruritus ani, who had failed to improve with perineal care, were treated by a single surgeon. All patients received intradermal injections of methylene blue. Endpoints were patient symptom score, and complications (pain, dysaesthesia, skin necrosis, incontinence and anaphylaxis). Symptoms improved in 96% and resolved in 57% of patients after one treatment. All four patients who had a second treatment became symptom-free. Seven patients noticed changes in continence, all resolved between 10 days and 6 weeks. Two patients were distressed by their decrease in their perianal sensation. There was no skin necrosis or anaphylaxis. Treatment of refractory pruritus ani by intradermal injection of methylene blue is effective and generally well tolerated.