Exogenous photodermatoses

Exogenous photodermatoses is a type of skin reaction, which is caused by exposure to ultraviolet (UV) light from an outside source, known as exogenous UV exposure. The most common exogenous photodermatoses is polymorphous light eruption, which is an exaggerated inflammatory response that occurs after exposure to sunlight, but may also manifest after exposure to visible light or photosensitizing medications. This painful skin condition is characterized by an itchy, red rash that appears anywhere on the body, including the hands, arms, legs, and face. Ultraviolet light is divided into UVA, UVB and UVC sub-bands. UVA is the most prevalent form of UV light and has an energy level too low to cause direct damage to DNA, but is believed to initiate skin reactions. UVB on the other hand has an energy level high enough to directly cause DNA damage. Both forms of UV light can induce exogenous photodermatoses. The diagnosis of exogenous photodermatoses includes a thorough patient history to include recent medications, travel history, and whether the patient deliberately exposed their skin to UV light sources such as solariums or tanning beds. A patch test is also conducted and biopsies of the photodermatoses can be taken if required. Treatment of this disorder is purely preventative. It involves avoiding UV exposure on abnormally-sensitized skin. Sunscreen with a high protection factor should be worn during the summer to avoid direct sunburn. Protective clothing and hats can also help to significantly reduce the risk of developing an exogenous photodermatosis flare-up. In extreme cases, photochemotherapy using PUVA (psoralen-uvatum a) therapy may be recommended, but this employs the same type of UV light which causes the skin reaction. It is important to be aware of exogenous photodermatoses and prevention is key. If these preventative measures fail and the rash appears, topical medications such as glucocorticoids and other anti-inflammatory therapies may be employed. Seeking prompt medical attention is important to avoid exacerbations of this condition.