What is the diagnosis and treatment for solar urticaria (hives caused by sunlight)?

From the Guidelines

Solar urticaria should be treated with a combination of sun avoidance, medication, and phototherapy, with the goal of improving quality of life and reducing morbidity and mortality. Treatment typically involves a combination of sun avoidance and medication. Patients should wear broad-spectrum sunscreen (SPF 50+), protective clothing, wide-brimmed hats, and avoid peak sun hours (10am-4pm) [ 1 ].

Key Considerations

• First-line medication includes non-sedating antihistamines like cetirizine (10mg daily), loratadine (10mg daily), or fexofenadine (180mg daily), which can be increased up to four times the standard dose if needed.
• For severe cases, omalizumab (150-300mg subcutaneously every 2-4 weeks) may be prescribed.
• Phototherapy using a gradual exposure protocol can help desensitize the skin in some patients, with PUVA and NB-UVB being potential options [ 1 ].
• During acute flares, oral corticosteroids like prednisone (20-40mg daily for 3-5 days) may provide temporary relief.

Phototherapy Options

• PUVA therapy can be effective in increasing the minimum urticarial dose (MUD) and improving sun tolerance, but it requires careful dosing and monitoring to avoid provocation, syncope, and anaphylaxis [ 1 ].
• NB-UVB has also been reported to be helpful in solar urticaria, with some studies showing improved sun tolerance and reduced symptoms [ 1 ].
• UVA alone or pre-PUVA UVA has been used in patients with a very low MUD, with increased MUDs and improved sun tolerance reported in some cases [ 1 ].

Important Considerations

• The choice of phototherapy should be governed by the action spectrum as determined by monochromator phototesting, and the minimum urticarial dose (MUD) should be determined before starting treatment [ 1 ].
• Treatment should be individualized based on the patient's specific needs and response to therapy, with the goal of improving quality of life and reducing morbidity and mortality.

From the Research

Definition and Symptoms of Solar Urticaria

• Solar urticaria is a rare type of photodermatosis that causes a significant impact on patients' quality of life (QoL) 2.
• It is characterized by erythema, whealing, and/or pruritus occurring minutes after sun exposure 3.
• Symptoms can be triggered by exposure to ultraviolet A (UVA), visible light, and/or ultraviolet B (UVB) 3, 4.

Diagnosis and Treatment of Solar Urticaria

• Diagnosis is typically made through photo-provocation tests to determine the action spectrum and minimal urticaria dose (MUD) 2, 3.
• Treatment options include:
  • Antihistamines, such as desloratidine, fexofenadine, and cetirizine HCl 3, 5.
  • Leukotriene receptor antagonists, such as montelukast 3.
  • Omalizumab, an anti-IgE antibody, for severe and recalcitrant cases 2, 6, 4.
• Treatment regimens can be tailored to the degree of photosensitivity and disease severity 2, 3.

Efficacy and Safety of Treatment Options

• A study found that 22 out of 23 patients achieved complete remission using a stepwise approach with antihistamines, leukotriene receptor antagonists, and omalizumab 2.
• Another study reported that 7 out of 8 patients experienced sustained remission of symptoms and signs using a combination of antihistamines and leukotriene receptor antagonist 3.
• Omalizumab has been shown to be effective in treating solar urticaria, even in cases where traditional therapies have failed 6.