Diagnosis is typically clinical, based on history and exam
Grading system: National Cancer Institute Common Terminology Criteria for Adverse Events(CTCAE)
Grade 1 - Aysymptomatic or mild symptoms, no intervention needed
Grade 2 - Moderate pain or ulcer that does not interfere with oral intake, modified diet indicated
Grade 3 - Severe pain, interfering with oral intake
Grade 4 - Life threatening consequences; urgent intervention indicated
Grade 5 - Death
Typically clinical diagnosis
Mucositis
Oral candidiasis
Myositis 
Herpes simplex virus infection
Dermatitis
Acute graft-versus-host disease
Alopecia
Conjunctivitis 