Photosensitivity is an abnormal reaction of
the skin to sunlight, especially to the sun’s ultraviolet (UV) rays. It results in skin rashes
that occur upon exposure to sunlight or other sources of ultraviolet radiation (UVR), such as fluorescent
lamps, tanning beds and sun lamps.
Skin
normally reacts to sun exposure by tanning or burning after a certain period of time. Photosensitive
reactions may appear as intense sunburns or hives. Depending on the severity of the condition, it may occur quickly or develop a few hours
after sun exposure.
Photosensitivity may be caused by an allergic
reaction to sun exposure that triggers an immune system response in certain sensitive individuals.
The reason for this type of immune system reaction is not known. These so-called sun allergies include polymorphous
light eruption and solar urticaria.
Risk factors for developing photosensitivity may include chronic skin conditions (e.g., rosacea) and use of certain medications (e.g., antibiotics).
In rare cases, photosensitivity is the result of a defect in the body’s ability
to repair skin cells that have been damaged by ultraviolet radiation. This only occurs in certain genetic diseases, such as
xeroderma pigmentosum and Cockayne syndrome.
To diagnose photosensitivity,
a physician may take a patient’s complete medical history, perform blood and allergy
tests to identify allergens and recommend medications such as antihistamines or
corticosteroids to relieve symptoms.
