Ulcerative dermatitis (scale rot) is seen in snakes and lizards kept in unhygienic conditions with excessive humidity and moisture. Moist, contaminated bedding allows bacterial and fungal growth that, when coupled with exposure to fecal degradation products and skin damage from inappropriate floor heating, can predispose to small cutaneous erosions. Secondary infection with Aeromonas spp, Pseudomonas spp, and a number of other bacteria may result in septicemia and death if untreated. Erythema, necrosis, and ulceration of the dermis, and an exudative discharge are common. Although lesions are often sequelae of skin injuries, they more often develop from within, as is the case with classic necrotic dermatitis in the ball python. The disease can develop even when these animals are maintained under pristine conditions, so it is not simply a matter of excessive moisture and poor hygiene. The condition starts with hemorrhage into scales, followed by pustules that eventually lead to open and ulcerated lesions. Debridement and treatment with systemic antibiotics, topical antibiotic ointment, and excellent hygiene and husbandry are essential.