Solar Urticaria: Understanding Sun-Triggered Hives in Canadians
Physical urticaria occurs when hives are triggered by a physical factor such as heat, cold, pressure, water, exercise, or sunlight. Some individuals with chronic hives (chronic urticaria) have an identifiable physical trigger.
Solar urticaria is a form of chronic hives triggered by sunlight. After sun exposure, the affected skin can develop redness, itching, or welts within minutes. The reaction typically fades after exposure stops.
Because sun exposure is common in outdoor work, sports, and recreation, recognizing this condition can help reduce confusion with sunburn or heat rash.
What Solar Urticaria Looks Like
Solar urticaria produces hive-like welts that appear on areas of skin exposed to direct sunlight. Unlike sunburn, symptoms are rapid in onset and may disappear shortly after avoiding further exposure.
Interesting differences include:
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Hives occur only on exposed skin
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Areas frequently exposed to sunlight may be less reactive
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Hives can occasionally develop under clothing (depending on fabric and UV penetration)
Why It Happens
Solar urticaria is believed to involve an immune response. Proteins in the skin change structure when exposed to sunlight, leading allergic antibodies to trigger hives. In rare cases, extensive sun exposure may lead to more severe systemic symptoms, including anaphylaxis.
Diagnosis
Diagnosis cannot be made on history alone. Other sun-related conditions such as polymorphous light eruption or certain porphyrias can mimic symptoms.
Dermatologists may perform tests that expose the skin to different wavelengths of light to determine the spectrum that triggers hives. Some individuals are diagnosed after controlled exposure to natural sunlight.
Treatment & Management
Symptoms may improve with:
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Oral antihistamines
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Topical steroid creams (e.g., hydrocortisone)
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Oral corticosteroids for more severe flares (e.g., short courses of prednisone — physician guided)
Some patients undergo controlled desensitization therapy, in which skin is gradually re-exposed to sunlight under professional supervision.
First Aid & Emergency Awareness
Solar urticaria is typically uncomfortable rather than dangerous, but anaphylaxis can occur in rare cases when large areas of skin are exposed. First aid education — including recognition of allergic reactions and emergency response — is valuable for Canadians who work or recreate outdoors.
Training through St. Mark James Training can help individuals, workplaces, and community organizations respond confidently to allergy-related emergencies. Combining first aid with CPR/AED certification is common across Canadian workplaces, camps, and sports environments.
Educational Disclaimer
This article provides general public education for Canadians. It is not a diagnostic tool or medical treatment guide. Seek assessment from a healthcare professional if symptoms persist, worsen, or interfere with daily activities. Call 9-1-1 in Canada for symptoms of anaphylaxis.