Irradiation Dermatitis – A Comprehensive Guide

Overview

Irradiation dermatitis (also called radiation dermatitis or radiodermatitis) is an acute or chronic skin reaction that occurs after exposure to ionizing radiation, most commonly during cancer radiotherapy. The condition ranges from mild erythema to severe ulceration and necrosis, depending on the dose, fractionation schedule, and individual susceptibility.

It affects anyone receiving therapeutic radiation—approximately 70–95 % of patients undergoing external‑beam radiation therapy develop some degree of skin toxicity. The prevalence is especially high for breast, head‑and‑neck, pelvic, and skin cancers, where the radiation field includes a large surface area of skin.

While most cases are self‑limited and resolve after treatment ends, severe forms can significantly impact quality of life, delay cancer therapy, and lead to long‑term scarring.

Symptoms

Skin changes typically appear within a few days to weeks after the start of radiation. The severity follows the Common Terminology Criteria for Adverse Events (CTCAE) grades 1‑4.

Early (Acute) Symptoms – usually during or within 2 weeks of treatment

• Erythema (redness) – skin looks sunburned; may feel warm.
• Dry desquamation – fine, flaky skin that peels like a mild sunburn.
• Itching (pruritus) – can be intermittent or constant.
• Tenderness or burning sensation – especially when clothing rubs the area.

Intermediate Symptoms – 2–4 weeks into therapy

• Moist desquamation – weeping, tender patches that may ooze clear fluid.
• Edema (swelling) – soft tissue may feel puffy.
• Pain – ranging from mild discomfort to severe, limiting movement.

Late (Chronic) Symptoms – weeks to months after radiation

• Fibrosis – thickening and hardening of the skin and underlying tissues.
• Telangiectasia – small, visible blood vessels that give a “spider‑vein” appearance.
• Hypopigmentation or hyperpigmentation – lighter or darker patches that may be permanent.
• Atrophy – thinning of the skin, making it fragile.
• Ulceration or necrosis – rare but serious breakdown of skin with risk of infection.

Causes and Risk Factors

Radiation damages DNA in both cancer cells and normal skin cells. The skin’s response depends on the total dose, dose per fraction, beam energy, and the volume of skin exposed.

Primary Causes

• External‑beam radiotherapy (EBRT) – most common source (linear accelerators, cobalt‑60).
• Brachytherapy – radioactive seeds implanted close to the tumor (e.g., prostate, cervical cancer).
• Total body irradiation (TBI) – used before bone‑marrow transplantation.

Risk Factors

• Higher total dose (> 50 Gy) and larger dose per fraction.
• Large treatment fields – breast, pelvis, scalp.
• Concurrent chemotherapy – especially taxanes, fluorouracil, or platinum agents, which sensitize skin.
• Patient‑specific factors:
  • Skin type – fair skin (Fitzpatrick I‑II) is more prone to erythema.
  • Smoking – impairs microvascular healing.
  • Diabetes, peripheral vascular disease – reduce tissue perfusion.
  • Obesity – increases friction and moist heat under garments.
  • Previous radiation to the same area – cumulative damage.
• Improper positioning or bolus use – a tissue‑equivalent material placed to increase dose to superficial skin can inadvertently raise dermatitis risk.

Diagnosis

Diagnosis is primarily clinical, based on visual inspection and patient‑reported symptoms. No specific laboratory test is required, but investigations may be ordered to rule out infection or differentiate from other dermatoses.

Clinical Assessment

• Inspection of the irradiated field for erythema, desquamation, ulceration.
• Documentation of grade (CTCAE or RTOG scale).
• Evaluation of pain level, functional limitation, and impact on quality of life.

Ancillary Tests (when indicated)

• Swab culture – if the area is weeping or appears infected.