Another kind of a rare photosensitive disorder is solar urticaria, which is also termed as the “allergy to the sun”. Unlike erythropoietic porphyria where light causes the activation of porphyrins causing symptoms of photosensitivity, solar urticaria is thought to be due to an antigen-antibody reaction in the serum of an affected individual.

Classification and Symptomatology

This rare skin disease is proposed to be caused by a hypersensitivity reaction between IgE antibodies and certain photoallergens found in the affected person’s blood. There are two classifications of solar urticaria:

• Type I is caused by a particular abnormal photoallergen present only in SU patients;
• Type II is caused by photoallergens that can be present in both SU patients and healthy individuals.

Solar urticaria usually presents as constant itching, burning sensation, and hives on skin areas that are exposed to sunlight. It commonly affects the arms, face, and neck. Within minutes, sunlight will set off itchiness gradually followed by rashes and edema causing large wheals. There have also been reports of tongue and lip swelling. Although these may not pose a fatal risk to a person, the effects are however debilitating. In severe cases, large edematous areas may cause intravascular fluid to shift into the skin that may result to decreased intravascular volume and blood pressure. This causes lightheadedness, nausea, and fainting. Bronchospasm is considered rare. In rare situations, solar urticaria may result to an anaphylactic reaction.

What You Doctor Can Do For You

The diagnosis of solar urticaria is based on the appearance of wheals in areas that are exposed to sunlight. Patients are more likely to report pruritus (itching) in the face. But this is not definitive as another photosensitivity disorder called Polymorphous Light Eruption (PMLE). Phototesting is the more confirmatory laboratory procedure.

Treatment of the condition varies depending on the severity of the reaction. Supportive measures may be implemented to restore the blood pressure and maintain adequate ventilation. Medications will include antihistamines and immunosuppressants. The patient may be subjected to phototherapy to desensitize the immune system from the light stimulus. For the meantime that the patient still did not develop tolerance to sunlight, he or she may be advised to use sunscreen and wear long sleeves and long pants to protect the skin. Plasmapheresis may also be considered for very severe cases.

What You Can Do

Like most allergic reactions, you should get yourself tested for the triggering factor. Avoidance is still the best measure to prevent and allergic episode. This can be done by wearing protective clothing and sunscreen when you are out under the sun.