Acne vulgaris is a disease of the sebaceous follicle which affects up to 90% of adolescent patients. Topical retinoids, benzoyl peroxide and antibiotics are the main treatments for mild to moderate acne vulgaris. The use of such topical treatments is often associated with local irritation and dryness making the skin more sensitive to the sun. The aim of our study was to assess the efficacy and skin tolerability of a fixed-dose combination therapy with hydrogen peroxide (4%), Salicylic acid (0.5%) and D-panthenol (4%) (HSD) gel, in mild-moderate acne vulgaris, during the period of sun exposure.We retrospectively observed 30 patients of Central Italy with mild to moderate acne between April and September 2012. All the patients selected underwent only therapy with HSD gel once a day in the evening for 60 days, while in the morning they just applied SPF 50 sunscreen. We evaluate the efficacy at 30 and 60 days with the "Global Evaluation Scale" (GES) and the tolerability with a 0-3 qualitative scale.The mean GES value showed a statistically significant reduction: 2.03 (SD 0.81) at baseline, 1.63 (SD 0.81) and 0.90 (SD 0.71) respectively at 30 and 60 days (p < 0.01). 21 (70%) and 27 patients (90%) did show good or very good tolerability at 30 and 60 days respectively.Topical treatments with retinoids, antibiotics and antiseptics may increase skin irritation reducing patient adherence to the treatment. HSD gel has shown a good skin tolerability and efficacy in reducing acne lesions, even during the sun exposure period in which traditional treatments should be cautiously used.