Also known as photosensitivity, a sun allergy occurs when the skin is hypersensitive to ultraviolet (UV) rays, which the sun naturally emits. The allergy can range from mild to severe, possibly causing more serious symptoms or limiting everyday activities. Some people have a hereditary type of sun allergy. Others develop symptoms only when triggered by other factors.
Researchers aren't sure how many people sun allergies affect, but an estimated 2% to 18% of people worldwide may live with a sun allergy. To learn more about it, check out the following slides.