Solar urticaria, also called sun allergy rash, is a rare dermatological condition. People with this condition develop an itchy, red rash when their skin is exposed to sunlight.

If solar urticaria is left untreated, it can cause pain, distress, and embarrassment. So, what treatments are available for this condition?

This article looks at the symptoms and treatments of solar urticaria as well as the various treatment options available to help manage solar urticaria symptoms.

  • There are treatment options available for solar urticaria including medication, which help people manage their symptoms.
  • The main symptom is a skin rash that can appear within minutes of exposure to sunlight.
  • The best way to prevent solar urticaria is to limit exposure to sunlight.
  • Solar urticaria can be hard to diagnose. It is rare and can look similar to other dermatological conditions, such as polymorphic light eruption.
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Solar urticaria is a rash that occurs on the skin after exposure to sunlight.

It is a rash caused by the sun that can affect anyone at any age, but most commonly occurs in people aged 20-40.

Solar urticaria is different from heat rash, which occurs due to humidity. Solar urticaria is a specific response to the ultra violet rays (UV) in the light itself, rather than a response to heat.

Typically, skin that is often exposed to the sun does not react or does not react severely. The solar urticarial rash tends to occur on skin that is rarely uncovered. It can also affect people through their clothing if the fabric is thin.

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Solar urticarial is characterized by a red rash that may sting or feel itchy.

The rash in solar urticaria can be red, itchy, and uncomfortable. Each urticaria is a distinct circular bump. The rash is made up of clusters of these bumps that cover the exposed skin.

As swelling happens quickly, the rash looks quite aggressive and sore. It can sting and be quite distressing for the person experiencing it.

The symptoms of solar urticaria are:

  • a red rash that appears on the skin after exposure to sunlight
  • itching
  • stinging pain
  • a rash that disappears within a few hours of ceasing sun exposure

In severe cases, people with this condition may experience secondary symptoms.

These include:

The rash can occur within minutes of skin being exposed to the UV rays in sunlight, which is why it has the name solar urticaria. According to the British Association of Dermatologists, there are three types of light UV light responsible for solar urticaria:

  • long wavelength ultraviolet (UVA)
  • short wavelength ultraviolet (UVB)
  • visible light (sunlight not containing ultraviolet)

People with this condition can also experience symptoms when:

  • skin is exposed to artificial light sources that contain UV
  • skin is covered by thin clothing that sunlight can pass through

What causes the reaction?

Research into solar urticaria is ongoing, and the exact cause of the response to UV has not been established. However, it is understood to be a type of allergic reaction, known as allergic hypersensitivity.

The reaction occurs between the UV radiation and a type of chemical in the body, known as a photoallergen. The specific chemical that acts as a photoallergen remains unidentified.

Discovering this will help researchers better understand what causes the condition and may lead to more effective treatment and prevention of solar urticaria.

What causes the symptoms?

The reaction sends a chemical signal to particular cells in a person’s skin, telling them to produce histamine. Histamine is the body’s way of trying to get rid of the allergen that is causing a reaction.

Histamine works by causing the skin to swell and itch. Itching is a response that compels a person to scratch away any allergens, which is why hives appear, and a rash develops.

What aggravates the condition?

For some people with solar urticaria, sensitivity to a chemical substance on the skin could contribute to the reaction. Substances that can cause sensitivity include:

  • skin care products
  • dyes
  • sunscreens
  • detergents

Avoiding these irritants can help to reduce the severity of the reaction. If chemical sensitivity is the primary cause, ceasing to use certain products may stop the rash developing altogether.

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Various tests may be used to diagnose solar utricaria, including a photopatch test where allergens are applied to the skin, and are then exposed to UV light.

A doctor can diagnose solar urticaria using the following tests:

  • Diagnostic phototest – test where small areas of skin are exposed to different strengths of UV light. Doctors observe the skin to see if the specific rash reaction seen in solar urticaria develops.
  • Photopatch test – a test where small patches containing different allergens are applied to the skin. When they are removed, the skin is exposed to light, and doctors note any reaction.
  • Photoprovication test – patches of skin are exposed to different types and strengths of UV light over several days. Doctors observe any reactions.

Methods or management and treatment include:


These drugs help combat the histamines that cause the rash and can reduce the redness, stinging, and itching. Antihistamines are the best way to treat solar urticaria in the short-term as they provide quick relief from the main symptoms. However, they do not help to prevent the allergic skin reaction from happening.


Desensitization is a long-term treatment that aims to prevent the allergic skin reaction from happening. Desensitization involves treating the skin with a course of UV light exposure (phototherapy) to try to desensitize it. Over time this can prevent rash developing on exposure to light, or make it less severe.


Immunosuppressant drugs suppress the immune response that occurs when the skin reacts, preventing histamine being produced. These are potent drugs that may have other side effects. So, this course of treatment is only ever short-term and is only recommended for extreme cases.

Dietary changes

It could be that something in a person’s diet is aggravating the reaction to sunlight. They may find removing potential allergens from their diet helps. However, this is a complementary treatment as opposed to the first course of action. More research needs to be conducted to say whether diet is a key factor in this condition.

The following methods can help a person avoid exposure to sunlight:

  • wearing loose, dark clothing that covers as much skin as possible
  • wearing hats with wide brims
  • carrying a parasol
  • sitting in the shade
  • trying to avoid going out during the day