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Sun Allergy: What is Solar Urticaria?

Madeehah Reza, Pharmacist, MPharm | Aug 15, 2022

A sun allergy occurs when you get rashes from sun exposure. There are a few types of sun allergies, including polymorphic light eruption (PMLE) and solar urticaria. Certain products or medications can also make sun-exposed skin prone to rashes or sunburn.

You can treat the symptoms of a sun allergy using self-care tips and over the counter medication. You may also need prescription medication if your symptoms are persistent.

If you’re exposed to strong sunlight for a long time, you can also risk heat stroke, migraines or sunburn.

In this guide, we’ll discuss:

What causes a sun allergy?
What are the symptoms of sun allergy?
Are there different types of sun allergies?
How is solar urticaria diagnosed?
How to prevent a sun allergy reaction
Treatments for sun allergy

What causes a sun allergy?

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The actual cause of a sun allergy is not known. The allergy might be caused by ultraviolet (UV) light, which may change a chemical in your skin which triggers an allergic reaction.

This is called an antigen-antibody reaction. In this reaction, your immune system produces antibodies to fight the foreign substance (the antigen). This reaction causes inflammation, which results in rashes or hives.

Women are more likely to have a sun allergy than men. You can get a sun allergy at any age and skin colour. If you have lighter skin, you’re more likely to be affected. You cannot pass on a sun allergy to anyone else or get skin cancer from having a sun allergy.

An effective way of preventing sun allergies is to apply sunscreen before going outdoors and wearing protective clothing. Not only will this help prevent sun allergies, but will also help prevent skin cancer.

Symptoms of a sun allergy

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The main symptom of a sun allergy is an itchy or burning rash. This rash can appear after sun exposure – it could take as little as 20 minutes to cause a rash. You might also have a delayed allergic reaction where the rash will appear two or three days after exposure.

You’ll see the rash on the areas of your skin that were exposed to the sunlight. This might be your face, neck, chest or arms.

A sun allergy rash can have different appearances. These include:

Small red spots
Red or white bumps (like hives)
Red areas with blisters that can turn into large, dry patches

While the rashes can look similar, a PMLE rash usually occurs a few hours after sun exposure. Solar urticaria, however, can happen within minutes of exposure.

Rarely, you may also get other allergy-related symptoms, such as feeling sick, dizzy or difficulty breathing, if large areas of skin are exposed.

A sun allergy is different to a heat rash. A sun allergy is caused by an allergic reaction to a chemical in your skin. A heat rash happens when the pores of your skin are clogged with sweat which leads to irritation.

It’s essential to stay safe when you’re out in the sun. Strong sunlight can lead to headaches and migraines or prickly heat (heat rash), especially during the summer months.

If you think you have a heatstroke, contact 999 immediately. Feeling sick, dizzy, having a headache or temperate over 40 ॰C after being exposed to strong sunlight for too long can signify heatstroke. though it affects everyone differently.

Are there different types of sun allergies?

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There are several different types of sun allergies. Many of them are rare, but some may be more likely to affect you than others. The more common types of sun allergies include:

Type of sun allergy	How does it affect the skin?	Does it affect me?
Actinic prurigo	A hereditary condition that makes your skin more sensitive to UV light. It can lead to skin rashes that take hours or days to form. It can also affect skin not exposed to the sun	Typically affects those of Native American origin
Solar urticaria	Urticaria will show as welts or hives (raised, red bumps), usually within minutes of sun exposure	It can affect a wide range of people
Polymorphous light eruption (PMLE)	Dry, itchy skin patches or blisters that form hours after sun exposure	More common in women, young adults and people with lighter skin
Drug-induced photosensitivity	Certain medications can make your skin more sensitive to sunlight and increases the risk of sunburn or skin allergies	If you take: Tetracycline antibiotics like doxycycline Fluoroquinolone antibiotics like ciprofloxacin Certain nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen Furosemide (diuretic) Isotretinoin (for acne) Amiodarone Diltiazem Quinine
Photoallergic reaction	Allergic reaction to certain chemicals or substances that are applied to the skin and then exposed to the sun. Blisters can leave behind a scar or mark	Products that can cause a photoallergic reaction include: Perfumes or fragrances Certain sunscreens Products that contain coal tar Disinfectants

How is solar urticaria diagnosed?

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Solar urticaria is diagnosed based the appearance of your rash, how quickly it appeared after sun exposure, and by using phototesting. During phototesting, your skin will be exposed to different UV and visible light wavelengths. These are the wavelengths of light that are found in sunlight.

Phototesting helps doctors determine what kind of light is causing your rash. A phototesting appointment can last between 45 minutes to an hour and a half. The test is not painful.

Solar urticaria does not usually last for more than a day. The rash often disappears once you protect yourself from exposure to the sun. If your GP suspects you have solar urticaria, they may refer you to a dermatologist for further tests.

If you’re unsure if you have solar urticaria, you can speak to a pharmacist at your nearest LloydsPharmacy. They’ll review your symptoms and offer appropriate advice and/or treatment.

How to prevent a sun allergy reaction?

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You can prevent getting a sun allergy by staying safe in the sun. Prolonged exposure can increase your risk of other health conditions, like skin cancer.

Avoid direct sunlight, especially during the day when it’s the strongest
Wear protective clothing, like long sleeves, trousers or hats
Always wear sunscreen with at least SPF 30 when going outdoors. You should apply sunscreen every two hours, and after swimming, sweating or showering

Try to build up your tolerance to the sun at the start of spring. This way, your skin will get used to the sunlight, and you’ll have a lower chance of a reaction when the sunlight becomes stronger. If you have PLE, you should discuss with your doctor how to build up your tolerance, to ensure you do it in a safe way.

If you’re taking any medication that you think is causing increased sun sensitivity, speak to your pharmacist or doctor.

Treatments for sun allergy

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There are several medicines you can use for the treatment of sun allergy. If you have an itchy rash, you can take antihistamine tablets or use creams like E45 Itch Relief or Eurax. At LloydsPharmacy, we have a range of products that treat allergic symptoms.

You may also need to take further treatments depending on your type of rash.

Type of sun allergy	Treatment
Actinic prurigo	Use emollients as often as possible to moisturise your skin. You may be prescribed corticosteroid creams to reduce inflammation. If your symptoms are severe, your doctor may consider prescribing hydroxychloroquine, an anti-inflammatory medication
Solar urticaria	Corticosteroid creams that bring down the inflammation of the rash, like hydrocortisone or Betnovate
Polymorphous light eruption (PMLE)	Use a cold compress on the affected areas of skin, which will cool down the rash and reduce the burning sensation
Drug-induced photosensitivity	Speak to a doctor or pharmacist first who may discuss with you the potential for stopping the medication
Photoallergic reaction	Speak to your doctor or pharmacist about any new products you suspect are causing the reaction, so they can recommend if you should stop using them and how to do so safely

A final note on sun allergies

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While there’s no cure for a sun allergy, you can take the proper precautions to protect your skin. Taking care while in the sun and using products like sunscreen and protective clothing can prevent UV light from damaging your skin.

You can find more tips and advice on skincare at our LloydsPharmacy blog, including sun care for eczema-prone skin and contact dermatitis.