Ozone therapy has been proving to be extremely effective in the treatment of injuries, aiding in blood circulation and, thus, providing better oxygen supply to the body. The objective of the following study was to report the case of a dog, female, mixed-breed, approximately 6 months old, presenting an extensive lesion in the left dorsal region, caused by pharmacodermia. The chosen treatment method was ozone therapy through the bagging method, associated with rectal insufflation, dressing and ozonated sunflower oil throughout the entire length of the lesion. It is possible to conclude that there was excellent healing of the lesion in a short period of time. Therefore, ozone therapy proved to be extremely efficient in the treatment of lesions with difficult consolidation.