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Solar Urticaria: An Overview of Sun Allergy

Reviewed by: HU Medical Review Board | Last reviewed: August 2022

Some people may experience a sensitivity to sunlight called a sun allergy, or photosensitivity. There are several types of sun allergies. One rare type is called solar urticaria. About 4 to 8 percent of all people with sun allergies have solar urticaria.1

What is solar urticaria?

Solar urticaria is a condition caused by an abnormal reaction to sunlight. Like any allergy, this happens because the body is overreacting to something. Experts think the sun activates a substance in the skin that turns it into an allergen (photoallergen). This reaction causes inflammation and other symptoms. But experts still do not know why some people have this reaction to sunlight.1,2

One feature that sets solar urticaria apart from other sun allergies is how quickly symptoms appear. For example, a common type of sun allergy is called actinic prurigo. In actinic prurigo, symptoms may take as long as 2 hours after sun exposure to appear. With other sun allergies, symptoms may even take days to appear. By contrast, with solar urticaria, symptoms may begin within minutes of sun exposure.1,3

People with solar urticaria also may be more sensitive to any sunlight exposure than people with other sun allergies. Research has shown that even sunlight that comes through glass or windows can trigger the symptoms of solar urticaria.4

What are the symptoms of solar urticaria?

The symptoms of solar urticaria can range from mild to severe. The most common symptom of solar urticaria is hives that appear after direct sunlight exposure. Other symptoms include:2,3

  • Red skin
  • Stinging or burning feeling in the skin
  • Itchy skin
  • Swelling

How serious the symptoms are depends on how long and intense the exposure was. Skin that is usually covered with clothing is more sensitive than skin that is usually exposed to the sun. Skin symptoms usually go away a few hours after the sunlight exposure.2

In rare cases, solar urticaria can cause symptoms besides the skin reaction. These include:2

  • Dizziness
  • Nausea
  • Tiredness
  • Headache
  • Flushed skin

How is solar urticaria diagnosed?

There are many conditions that can cause a skin reaction after exposure to the sun. This may make it difficult to get an accurate diagnosis for solar urticaria. Tracking your symptoms and noting when they appear is helpful information that may help your doctor diagnose you.1

One test your doctor may use to make a diagnosis is phototesting. In this test, your doctor exposes a small part of your skin to ultraviolet (UV) light. UV is the part of sunlight that causes a reaction in the skin. The controlled exposure to UV light used in phototesting helps your doctor study your body's response.1

Your doctor may also conduct other blood tests to rule out other conditions.1

How is solar urticaria treated?

In mild cases, taking precautions to avoid the sun may be enough to manage solar urticaria. Removing yourself from the sun will typically cause symptoms to go away quickly. But there are also drugs that may help reduce symptoms.1

Mild to moderate cases

Antihistamines are a very common allergy drug that are available over the counter. Discuss dosing with your doctor, as they may prescribe higher doses than the instructions on the box say.1

Your doctor also may prescribe a steroid ointment or oral steroids for you. Use these exactly how your doctor prescribes them. These drugs are available only by prescription.1

Severe cases

For severe cases that do not respond to the above therapies, your doctor may recommend phototherapy. Phototherapy involves slowly exposing your skin to UV light. The process is done in your doctor's office in a controlled way. Phototherapy slowly lessens how sensitive your skin is to the sun.1

Another treatment for severe solar urticaria is a biologic drug called omalizumab (Xolair®). This is an injectable drug prescribed for people with asthma or chronic hives.5

All treatments may have side effects. Side effects can vary depending on the specific treatment or drug. Before beginning treatment for solar urticaria, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you take. This includes over-the-counter drugs.

Managing your solar urticaria

One of the best ways to manage any sun allergy is by protecting yourself from the sun. There are many ways to do this, such as:1

  • Stay inside and away from large windows during the brightest parts of the day.
  • Wear clothes and hats that cover most of your skin.
  • Apply non-irritating sunscreen with a sun protection factor (SPF) greater than 30.
  • Use a lip balm with high SPF on your lips.
  • Wear sunglasses to protect your eyes.

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