A man in his 60s with gastric cancer presented to an urgent care center with mouth pain. He had initiated capecitabine chemotherapy (oral prodrug of fluorouracil) prior to his visit. Eating exacerbated the pain, although he could still eat solid food. He reported no fevers or chest pain. On examination, he was afebrile. Oral examination showed generalized erythema and some shallow ulcerations without bleeding. No signs of bacterial, viral, or Candida infection were present. He was not neutropenic. He was diagnosed with chemotherapy-associated grade 2 oral mucositis (World Health Organization scale, range 1-4, with 1 indicating soreness with or without erythema and 4 indicating no alimentation possible).