Dermatology - Solar Urticaria

This leaflet has been written to help answer some of your questions about solar urticaria. You may have been given this leaflet because you have been diagnosed with solar urticaria or because we think this might be the cause of your symptoms.

What is solar urticaria?

Urticaria generally is a common skin reaction that can affect about 2 in every 10 people at some time in their lives. Other common names for urticaria are “hives”, “nettle rash”, “wheals” and “welts”.

Solar urticaria is a much rarer type of urticaria that is caused by sunlight. Patients with solar urticaria have itchy or burning skin after they have been out in the sun. They may notice pink or red patches which can become swollen and look like nettle stings.  The patches can be of different shapes and sizes. If the patient comes out of the sun the rash will disappear quite quickly (often within an hour). The skin looks completely normal after the rash has gone.

Who suffers from solar urticaria?

Solar urticaria is more common in women than men. It can start at any age, but most people seem to develop it before the age of 40.

What causes solar urticaria?

Everybody’s skin contains special immune (allergy) cells called mast cells. In solar urticaria, these cells release a chemical called histamine and other chemicals, which can lead to the skin becoming red, swollen and itchy. This may be triggered by a kind of allergic reaction in the body, but it is not known why this happens in certain people. Occasionally solar urticaria can be triggered by certain medications but this is uncommon.

Is solar urticaria serious?

Solar urticaria can be serious if you expose large areas of the body to sunlight (e.g., sunbathing). Exposing large areas of your skin to sunlight can make you feel lightheaded, sick and turn pale. There have been reports of one or two swimmers collapsing because they exposed a large area of their body to sunlight.  Having an episode of solar urticaria can also make some people feel generally unwell; for instance, they may feel tired or develop a headache.

Is solar urticaria infectious?

No. There is no risk of other people catching solar urticaria from you.

Does having solar urticaria increase your risk of cancer?

No. Experts think solar urticaria is more like an allergy.

Is solar urticaria hereditary?

No. Experts do not believe solar urticaria is hereditary.

Can solar urticaria be cured?

No treatment will completely get rid of solar urticaria, but by careful sun avoidance, use of sunscreens and antihistamines the rash can be reduced. Other treatments can be considered if this approach is not enough to control the symptoms (see below).  Sometimes solar urticaria can go away on its own, but it usually lasts for quite a long time.

How will having solar urticaria affect me?

If you have been diagnosed as having solar urticaria you may have to make changes to your lifestyle, which can be restrictive. The doctor can prescribe antihistamine tablets which will help to control the rash, but you should also try to:

• Avoid the sun during conditions that provoke your photosensitivity and particularly when sunlight is intense. In the UK this is mainly between 11am and 3pm, although other times of day can be troublesome
• Wear protective clothing, with close/tightly woven fabrics, long sleeves and trousers, hats with broad brims. Glasses and sunglasses with wrap around lenses can also be helpful
• Use a sunscreen that is SPF 30 or above (high UVB protection) and also has high UVA protection. Remember to re-apply the sunscreen evenly and often
• Learn how much sunlight your skin can tolerate and keep within that limit
• Make sure you introduce your skin to sunlight gradually in the spring

What about other artificial light sources?

Some patients with solar urticaria need to be careful around bright artificial light sources. This can include the blue-ish lights that dentists sometimes shine into your mouth. You should mention to your dentist that you have been diagnosed with solar urticaria.

The lights that some beauticians use when applying artificial fingernails may also trigger a reaction.

You should not use a sun bed if you have a sun allergy.

What about vitamin D?

Importantly, for people to make enough Vitamin D themselves, they need a certain amount of sun exposure. The sun protection measures needed for people with solar urticaria mean Vitamin D deficiency is a real risk and this does require treatment with supplements if it occurs. Your vitamin D levels can be monitored through blood tests.

How can solar urticaria be treated?

Sunscreens

You will be provided with sunscreens on prescription, and these will help prevent the rash developing. Sunscreen should be applied as thickly and evenly as possible and re-applied often.

Antihistamines

Antihistamines block the effects of histamine and will help to reduce the rash and itching. It is best to take your antihistamines regularly as prescribed by your doctor. There are many different types of antihistamine. Some of the older types can cause drowsiness but this is less likely with the newer ones. You may need to try different antihistamines until you find the one that suits you best. You may need to take quite high doses of the antihistamines for the greatest benefit.

Desensitisation or UV Treatment

Sometimes the resistance of your skin to the effects of the sun can be increased by ultraviolet light. This is done in a hospital department and will involve visiting the hospital three times a week for about 5 weeks in the spring. It involves gradually exposing your skin to a little more ultraviolet light every visit to try to build up your skin’s resistance. The effects of desensitisation are lost in the winter so you will have to build up your resistance again in the spring. It is not suitable for everybody, as it depends on the particular wavelengths of light that a person reacts to.

Omalizumab

Omalizumab is an injection based treatment that targets a molecule which makes the mast cells in the skin react. It does not suppress the immune system as it works in quite a specific way, but there is the possibility of side effects, so the risks and benefits of the treatment do need to be carefully considered.  Omalizumab is given every 4 weeks and is often very effective. However, people with solar urticaria are not all automatically eligible to receive this treatment currently.

Further information is available from the British Association of Dermatologists website at: https://www.bad.org.uk/pils/omalizumab/

Other Treatments

Some other options for solar urticaria can include tablet treatments such as ciclosporin. These are strong tablets affecting the immune system, and can have side effects, so the risks and benefits need to be carefully considered.

Hardening or Toughening

Some people with solar urticaria may be able to increase the resistance of their skin at home. This involves going outside for short periods in the spring to build up your resistance. You might find the time is as short as a few minutes at first, but you may be able to gradually build this up to longer times. You will have to be careful not to overdo it, but as you understand more about how much light triggers your rash, you will be able to judge how long to stay out. The effects of hardening are lost in the winter so you will have to build up your resistance again in the spring.  We have included an example of how you might try to toughen your skin in the spring.

Example:

Mrs Smith knows her solar urticaria rash usually appears after going outside for half an hour. Mrs Smith has been toughening her skin in the spring and this is her diary, please see example on next page.

Contact us

The Photobiology Unit can be contacted on 0161 206 4081 or by e-mail Photobiology.Salford@nca.nhs.uk