Health Topics A-to-Z
Sun Allergy (Photosensitivity)
What Is It? A sun allergy is an immune system reaction to sunlight, most often, an itchy red rash. The most common locations include the "V" of the neck, the back of the hands, the outside surface of the arms and the lower legs. In rare cases, the skin reaction may be more severe, producing hives or small blisters that may even spread to skin in clothed areas.