Polymorphic light eruption is not very common, but it does happen. It generally affects adult females aged 20-40, but it can also affect children and males. This skin condition in youngsters can be triggered by some medications that, for example, are used to treat acne. It may also disappear on its own after a period of time.
Most people do not need treatment, and those who do may take an oral antihistamine like hydroxyzine if itching is bothersome or diphenhydramine if the reaction becomes severe.