title: Protection factors are ratios.
authors.forename: A
authors.initials: A
authors.lastname: Young
authors.forename: S L
authors.initials: SL
authors.lastname: Walker
mesh_terms: D006801:Humans; D007108:Immune Tolerance / Q000187:drug effects; D013471:Sunburn / Q000276:immunology*; D013473:Sunscreening Agents / Q000494:pharmacology*
chemical_list: D013473:Sunscreening Agents