Radiotherapy is a common cancer treatment given to over 50% of cancer patients (Delaney et al. [29]). Radiotherapy can be given as a high‐dose treatment with curative intent or, usually at lower doses, may be used to provide palliation of cancer symptoms (see Chapter c24 for further information). A skin reaction from radiotherapy is one of the most common side‐effects of treatment and can cause considerable distress to the patient and compromise delivery of the planned dose (Schnur et al. [125]). However, severe skin reactions are only observed with higher doses and longer fractionations (number of treatments). Radiation used for palliation should never provoke a skin reaction beyond a brisk erythema.