Grade 1: painless erythema and erythema covering less than 10% BSA

Grade 2: tender erythema covering 10 - 30% BSA

Grade 3: erythema covering greater than 30% BSA and erythema with blistering; photosensitivity; oral corticosteroid therapy indicated; pain control indicated (e.g., narcotics or NSAIDs)

Grade 4: life-threatening consequences; urgent intervention indicated

Reference: Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0 Published: November 27, 2017