Anal fistula mainly refers to the presence of a noticeable fistula in the tissue under the perianal skin, which connects the inner opening in the anal canal and the outer opening around the anus. Usually, the anal fistula does not cause significant pain when it is not in acute flare-up. However, if the anal fistula enters an acute episode, there may be pain due to inflammation at the local external opening of the anus, and possibly an increase in purulent discharge, which can irritate the skin around the external opening, causing stinging pain and itching. To prevent recurrent episodes of anal fistula and further aggravation of the condition, it is advised to seek surgery as soon as the fistula is detected.