 In the United States, only about 4% of patients with photosensitive disorders are reported to have been diagnosed with solar urticaria.Internationally, the number is slightly larger at 5.3%.Solar urticaria may occur in all races but studies monitoring 135 African Americans and 110 Caucasians with photodermatoses found that 2.2% of the African Americans had SU and 8% of the Caucasians had the disease showing that Caucasians have a better chance of getting the disease.