Na sucrose octasulfate (Na SOS) was tested for ability to relieve radiation-induced acute skin and mucosal reactions in patients with head and neck cancer. Sixty patients were included in this prospective, double-blind, randomized study. Skin and mucosal reactions were scored using several variables. No statistically significant difference was found between the results with Na SOS and those with placebo for any of the variables, with the exception of skin desquamation, which showed a significant difference in the placebo group. The most likely explanation for this is that the Na SOS gel itself left behind a flaky layer that was difficult to distinguish from radiation-induced flaking. In conclusion, we cannot recommend Na SOS in the routine management of radiation-induced skin and mucosal reactions.