In a double-blind crossover study orally administered aspirin buffered with magnesium aluminum hydroxide significantly reduced ultraviolet light-induced erythema in ten adult male subjects when compared with magnesium aluminum hydroxide used as a placebo. This effect was most noticeable at four and six hours postirradiation but could be detected at 24 hours. Of the four subjects who complained of itching, aspirin relieved this symptom. The amount of aspirin taken (3.6 gm per day) was within the usual therapeutic dose.
The mechanism of this effect of aspirin is not known. A possible mechanism of action could be stabilizing lysosomes and the inhibition of kinins or enzymes.
Miller WS, Ruderman FR, Smith JG. Aspirin and Ultraviolet Light-Induced Erythema in Man. Arch Dermatol. 1967;95(4):357-358. doi:10.1001/archderm.1967.01600340017004