The reaction occurs from within a few minutes to up to several hours after UV light exposure. Though sunburn-like symptoms appear only on the parts of the body exposed to UV radiation, resulting skin damage can persist. For example, Henry Lim, M.D., reported in the March 1990 issue of Archives of Dermatology that several patients previously exposed to photoallergens continued to have phototoxic skin eruptions up to 20 years after discontinuing medication use, even though they avoided further exposure to the photoallergens. Because drug-induced photosensitivity disorder symptoms mimic sunburns, rashes and allergic reactions, many cases go unreported. Also, although research has shown that the numbers of photosensitized individuals may be high, most people do not associate the sun's light with the development of their skin eruptions.
Some medications can cause photophobia.
Although literally, photophobia is fear of light, photophobic photosensitivity disorder patients avoid light not because they're afraid of it but because their eyes are painfully sensitive to it. The degree of photosensitivity varies among individuals. Not everyone who uses medications containing photoreactive agents will have a photoreaction. In fact, a person who has a photoreaction after a single exposure to an agent may not react to the same agent after repeated exposures. On the other hand, people who are allergic to one chemical may develop photosensitivity to another related chemical to which they would normally not be photosensitive.