Radiation dermatitis (RD) results from radiotherapy and often occurs within the first 4 weeks of treatment, although late effects also occur. While RD may resolve over time, it can have a profound effect on patients' quality of life and lead to dose modifications. A study group of international, interdisciplinary experts convened to develop RD prevention and treatment guidelines based on evidence from randomized, controlled trials. Evidence-based recommendations were developed after an extensive literature review. Randomized, controlled trials with standardized measurement of outcomes were considered the best evidence, and a majority of the recommendations were formulated from this literature. The adoption of washing with water, with or without a mild soap, and allowing the use of antiperspirants is supported by randomized trials. Use of topical prophylactic corticosteroids (mometasone) is recommended to reduce discomfort and itching. There is some evidence that silver sulfadiazine cream can reduce dermatitis score. There is insufficient evidence to support, and therefore the panel recommends against the use of trolamine, topical sulcrate, hyaluronic acid, ascorbic acid, silver leaf dressing, light-emitting diode lasers, Theta cream, dexpanthenol, calendula, proteolytic enzymes, sulcralfate, oral zinc, and pentoxifylline. Moreover, there is no evidence to support the superiority for any specific intervention in a reactive fashion. For patients with established radiation-induced telangiectasia and fibrosis, the panel suggests the use of pulse dye laser for visual appearance, and the use of pentoxifylline and vitamin E for the reduction of fibrosis.