When a decision to undertake this is made, a small area of the frequently affected skin is exposed to varying doses of UVA and minimal erythema dose (MED) (amount of UV radiation that will produce minimal redness of skin within a few hours following exposure) of broadband UVB for three consecutive days. An examination of the skin to detect the rash is made, however, up to 40% have false negative responses. Biopsy findings
Depending on the clinical signs, histology of a skin biopsy may vary. There may be oedema in the epidermis with a dense superficial and deep lymphocytic infiltrate without vasculitis. Recently appearing lesions may show neutrophils. Spongiosis and vesicle formation may also be present. Direct immunofluorescence testing is negative. Differential diagnosis
The photosensitivity connected with lupus erythematosus is the main condition that may appear like PLE. However, the rash of lupus is inclined to be more persistent. PLE does not increase the risk of lupus.Other similar appearing conditions are solar urticaria, which has a shorter duration, the eczema-like condition, photosensitive dermatitis, and photosensitivity drug reaction.Prickly heat, which is caused by warm weather or heat is not the same as PLE.Photosensitivity is also found in some of the porphyrias. Nearly all cases of porphyria cutanea tarda exhibit blister formation on the skin within 2–4 days of light exposure. Variegate porphyria and hereditary coproporphyria can also exhibit symptoms of light-induced blisters.
This includes emotional distress, anxiety and depression

History
Thomas Bateman, following on from findings of his predecessor, Robert Willan, first recorded a description of PLE in the nineteenth century, defining it as eczema solare with recurrent non scarring eczematous lesions triggered by sun exposure.Danish physician Carl Rasch first described the eczema-like polymorphic light eruption in 1900, following his interest in the effect of sunlight on the skin. He has since been credited with coining the term "polymorphic light eruption". See also
Photosensitivity with HIV infection
List of cutaneous conditions

References
External links

www.emedicine.com