Radiodermatitis is an acute or chronic dermatological condition characterized by erythema, rash, desquamation, necrosis, fibrosis, and depigmentation of the affected skin. It develops as a consequence of exposure to radiation either during diagnostic radiological procedures, cancer treatment or environmental or occupational exposure.
Radiodermatitis is also known as radiation dermatitis/radiation-induced skin reaction (RISR) or radiation injury. It occurs following exposure to high doses of ionizing radiation. This can occur either when patients are irradiated for malignancies; during diagnostic or therapeutic procedures like coronagraphy or fluoroscopy and following nuclear disasters and occupational radiation exposure . Radiodermatitis is the most common complication of roentgen therapy in cancer patients  .
It typically develops several years following exposure but acute effects can also be seen subsequent to excessive radiation. The clinical presentation depends on the dose, duration, and extent of the area receiving the X-rays. Within 48 hours to 7 days after exposure, the affected skin becomes severely inflamed and patients present with redness, pain, burning sensation, and itching  at the site. These symptoms will usually aggravate, subside and then recur with erythema, swelling, and vesicles lasting for up to 30 days accompanied by pustules, and ulceration which can become infected  followed by desquamation and necrotic skin changes. Although healing is slow, the recovery is complete in most cases. In some patients, however, lesions may fail to heal especially, if the radiation dose is large.
Delayed effects of radiation, also known as chronic radiodermatitis, may appear up to several years after the end of treatment or exposure and include hypo or hyperpigmentation of the skin, atrophic changes, photosensitivity, telangiectasia and delay in healing of accidental or surgical wounds.
The diagnosis of radiodermatitis depends on the history, and physical examination. The affected individual will usually be able to provide detailed information about acute or long-term radiation exposure at work or for the treatment of a malignancy. A dermatological examination may reveal skin erythema, blisters, ulceration with sloughing in acute cases while hypo or hyperpigmentation with skin atrophy, patchy alopecia, telangiectasia, and fibrosis may be noticed in chronic radiodermatitis.
Biopsy of the affected skin for histopathological examination can help confirm the diagnosis but is rarely performed. As the incidence of secondary bacterial infection is high, a swab from the ulcerated skin for microbiological testing is useful for early detection and management  of the condition.
Several subjective grading tools are used to document radiodermatitis      . These tools are based on observations performed before starting treatment and then every week during and after completion of radiation therapy.