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Solar Urticaria: the Allergy to the Sun

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08 Jul 2024
2 Min

Solar urticaria is a rare photodermatosis that causes skin lesions, such as redness, itching and hives, within minutes of exposure to sunlight. Although it is considered uncommon in the general population, experts suggest that it may be under-diagnosed due to unrecognised symptoms.

Solar Urticaria Symptoms

Solar urticaria manifests rapidly, usually within minutes of exposure to sunlight. Symptoms include:

  • Reddening of the skin: Redness of the skin is seen in areas exposed to the sun.
  • Weals or lumps: Raised lesions on the skin that may vary in size.
  • Intense itching: Itching sensation in the affected areas.


In some cases, lesions may appear hours after sun exposure. The severity of symptoms generally increases with the intensity of sun exposure. The most affected areas are those directly exposed to the sun, such as the chest, back of the neck and shoulders. However, on the face and hands, there is often a phenomenon of light tolerance due to constant exposure throughout life, which makes the skin less reactive.

Differential Diagnosis

It is crucial to differentiate solar urticaria from other skin conditions in order to provide appropriate treatment. Some conditions with similar symptoms include:

  • Common sunburns: Sun urticaria appear within minutes after exposure to sunlight, while sunburns develop more slowly, usually hours after exposure.
  • Secondary photodermatosis due to medication: Certain medications may cause skin burns on exposure to the sun, especially in older people or those on multiple medications.
  • Polymorphous Light Eruption (P.L.E.): This is a sun-induced skin reaction that can manifest itself in different clinical forms. It usually appears in spring or early summer, when parts of the body that are generally covered during the rest of the year are exposed to the sun.
  • Lupus: it is an autoimmune disease that can manifest itself as an irregular rash on areas of the skin that are exposed to sunlight.
  • Actinic prurigo: This mainly affects older people and manifests itself as an exaggerated reaction of the skin to solar radiation, generally accompanied by thickening of the skin.


Solar Radiation Prevention

Prevention is key to combat solar urticaria. Some prevention measures include:

  • Use high sun protection: Apply sunscreen with a high sun protection factor (SPF) 30 minutes before sunbathing.
  • Avoid prolonged exposure to the sun: Limit time in direct sunlight, especially during peak radiation hours.
  • Protective clothing: Wear clothing that covers most of the body, wide-brimmed hats and sunglasses.
  • Consultation with a dermatologist: For proper evaluation and treatment, it is advisable to seek the opinion of a specialist.


Although solar urticaria is a rare condition, it is important to be informed about its symptoms and treatments in order to detect and address it properly. Protecting our skin and being aware of how it reacts to sunlight can significantly improve the quality of life of those suffering from this condition.

For more information on how to protect your skin from the sun, consult the CreuBlanca Dermatology Unit.