What Is Photosensitivity?
6. Investigations
Some of the investigations that may be useful include assessing urine porphyrin levels, and determining anti-Ro (SS-A) antibody and antinuclear antibody (ANA) levels. Other tests include photopatch testing, and phototesting with ultraviolet (UV) A, UVB, and visible light. In photopatch testing, two sets of suspected photoallergens are applied to the back. One set will be removed after 24 hours and both sets evaluated after 48 hours.
There is a positive reaction if there is the presence of vesicles, edema, and erythema. In phototesting, small areas on the back or inner forearm are treated with increasing doses of light. The minimum dose of light required to cause a reaction is called the minimum erythema dose (MED).
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