being tested and is not always effective. when the treatment is a success, the patient's photosensitivity is decreased to the degree that they can undergo puva which can result in the relief of the urticarial outbreaks for an extended period of time. the major setback to this treatment is that the side effects can be severe and may include anaphylactoid reactions. epidemiology 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. the age ranges anywhere from 5–70 years old, but the average age is 35 and cases have been reported with children that are still in infancy. solar urticaria accounts for less than one percent of the many documented urticaria cases. to put that into a better perspective, since its first documented case in japan in 1916, over one hundred other instances of the disease have been reported. history solar urticaria was first identified by p. merklen in 1904. just a year later, in 1905, ward became the first to induce urticaria through exposure to the sun in a controlled environment. the first documented case came in japan in 1916. the name "solar urticaria" was proposed in 1923. in 1928 urticaria was induced for the first time. this was carried out by phototesting with increasing amounts of radiation of varying wavelengths. in 1942 the disease was passively transferred to normal volunteers using serum from patients with solar urticaria.