UV exposure is closely associated with both melanoma and non-melanoma forms of skin cancer. The usefulness of sunscreen in lowering the incidence of skin cancer has been disputed, despite its widespread promotion as a crucial preventive tool. The methods by which sunscreens prevent UV damage are reviewed in this article, along with data from observational research, randomized trials, and meta-analyses. Limitations and debates (including the "sunscreen paradox") are also covered, and suggestions for best practices are given. The debate is backed up by references to more than 20 current scientific publications.