The aetiology of the radiotherapy-induced skin reaction (RISR) has been well documented (Hollinworth and Mann, 2010; Trueman and Taylor, 2014; Bostock and Bryan, 2016). In radiotherapy, external beam radiation is delivered in small doses (fractions) periodically over time. In theory, this allows healthy basal cells to recover between treatments. If skin damage occurs, this is cumulative, with symptoms of RISR usually showing 10–14 days after the start of treatment (Trueman, 2015).