 It "removes a circulating factor from the blood that may be involved in causing the urticaria," but is still 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.