Acute radiodermatitis occurs when an "erythema dose" of ionizing radiation is given to the skin, after which visible erythema appears up to 24 hours after.[4]:39 Radiation dermatitis generally manifests within a few weeks after the start of radiotherapy.[5]:143 Acute radiodermatitis, while presenting as red patches, may sometimes also present with desquamation or blistering.[8] Erythema may occur at a dose of 2 Gy radiation or greater.[9]