Which of the following can be classified as a skin disease?

Active herpes can be classified as a skin disease because it is a viral infection that manifests on the skin or mucous membranes, producing lesions and inflammation. Herpes is characterized by painful blisters in the affected areas, and it requires proper diagnosis and, often, medical treatment. This condition is caused by the herpes simplex virus and involves a repeated cycle of outbreaks, which solidifies its classification as a skin disease.

In contrast, sunburn is a reaction to excessive UV exposure, moles are benign skin lesions that do not indicate disease, and normal skin is simply healthy, functioning skin without any disease. These other options do not meet the criteria of a skin disease as they either reflect reactions, benign conditions, or the absence of disease.