Hi. Thanks for your query. Noted the history and understood the concerns. Since there is a history of external hemorrhoid surgery before the farting started there may be one of the following reasons: Gas producing bacteria overgrowth, may be secondary to antibiotics and other medications. Aerated drink, nuts, and many of the things in food or beverages can cause this hence you have to observe stringently about the causative factors and stop these altogether. Anxiety and stress can cause aerophagia and cause odorless farting. Also send the stool for tests and if infection is found a course of an antibiotic, metronidazole, probiotics can helps you to get rid of this problem.