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 and perform blood and allergy tests to identify allergens (substances the body mistakenly perceives to be a threat, triggering an allergic reaction).

Photosensitive reactions (e.g., papules, hives) may be treated like other skin rashes or sunburns with cool oatmeal baths or other measures. Physicians may also recommend medications such as antihistamines or corticosteroids to relieve symptoms.

For people with photosensitivity, avoidance is the best prevention method. Staying out of sunlight as much as possible can effectively reduce photosensitive reactions. When venturing out into sunlight, it is essential to wear a hat and clothing that covers as much skin as possible. Hypoallergenic sunscreen (made with ingredients that do not trigger allergic reactions) can be used to protect exposed skin.