<qa>  What is the most common side effect of tacrolimus?Tacrolimus and pimecrolimus may have fewer side affects than topical steroids. Recently, in an open label trial of 19 patients with recalcitrant erosive lichen planus, tacrolimus decreased the area of ulceration by 73 after an eight week course. Local irritation was the most common side effect. However, tacrolimus comes in an ointment base, a poorly tolerated vehicle for oral lesions. Topical treatment of oral lesions has also been compromised by problems with maintaining sufficient contact time between poorly adherent cream and ointment preparations and moist mucous membrane surfaces. 