Hydrogen peroxide is commonly used for cleansing superficial wounds, because of its antimicrobial action attributed to oxidizing capacity. The release of oxygen doping oxidation results in effervescence, which promotes a weak mechanical means of removing tissue debris. In the past, hydrogen peroxide was used for the management of meconium ileum and for fecal impaction because liberated oxygen tend to break up impaction and initiate peristaltic reflex. However, the stronger solution has a caustic action. The potential dangers of hydrogen peroxide enema were not so well known until 1950s when Pumphery recognized deleterious effects from such enema. During 1980s, hydrogen peroxide was used for disinfection of endoscope and several authors reported peroxide-induced colitis. We report a case of hydrogen peroxide induced chemical colitis in a 47-year-old man, who complained bloody stools and tenesmus after introducing hydrogen peroxide soaked gauss into the rectum to relieve pruritus am. Colonoscopy demonstrated diffuse erythema, edema and friability of rectal mucosa upto 6-7 cm from anal verge. The proximal margin of the lesion was well demarcated from normal appearing mucosa. Mucosal biopsy revealed histologic findings compatible with ischemic changes. His symptoms improved rapidly with conservative treatment.