Sun rash is a rare skin condition characterised by small groups of red blisters that occurs when the skin is exposed to sunlight. Sun rash can appear within minutes of exposure to the sun and can affect anyone at any age. While it often feels itchy and uncomfortable, sun rash usually settles quickly and isn't a sign of anything more serious.
Dr Roger Henderson looks at sun rash causes, symptoms, treatment and prevention tips:
What is sun rash?
Sun rash is a rare skin condition and completely different to the problem of prickly heat rash or a sweat rash. Medically known as solar urticaria, sun rash is believed to be due to a reaction to the ultraviolet (UV) rays in sunlight rather than heat from the sun.
People who suffer from sun rash may also experience symptoms if they wear thin clothing that sunlight can pass through, or if their skin is exposed to artificial light sources that contain UV light. Sun rash is different from prickly heat or a sweat rash which is linked to sweating, heat and humidity.
Sun rash risk factors
The exact reason sun rash affects some people more than others is not completely understood, but you are more at risk of sun rash if the following applies:
Aged 20-40 years old
Have a family history of sun rash
Live in Northern parts of the world
Have naturally light skin
Sun rash symptoms
The typical pattern of a sun rash is that it develops on a part of the skin after 30 minutes or slightly longer after being exposed to the sun.
Sun rash typically looks like small groups of red blisters that are uncomfortable and itchy, and it can feel as if the skin is burning and rough. It can be distressing to experience since the skin swelling happens quickly and can spread to anywhere the skin has been exposed to the sun.
If large parts of the body are affected by sun rash there may also be nausea, dizziness and headaches. The individual rashes can settle in less than 2-3 hours for many people (longer for others) but they usually come back again when the skin is exposed to the sun.
How is sun rash diagnosed?
Many sun rash cases can be diagnosed by a doctor simply from the history, and by looking at the rash if it is still present. If tests are required to confirm the diagnosis there are three main ones available:
Phototest: the first is a diagnostic phototest, where small areas of skin are exposed to different strengths of UV light and any reaction is observed.
Photopatch test: the second is a photopatch test, where small patches containing different allergens are put onto the skin and when they are removed the skin is exposed to light.
Photoprovocation: the third is a photoprovocation test where different types and strengths of UV light are shone onto different skin areas, and any reactions observed.
6 sun rash treatment tips
For most people, no treatment is necessary as by simply avoiding any sunlight the rash will slowly settle over a short time. However, if symptomatic relief is required possible sun rash treatments include the following:
1. Antihistamine tablets
These anti-allergy tablets work on the histamines that cause the rash and provide quick relief from symptoms. Always use a non-sedating type, and ask your pharmacist for advice on the best one for you. Antihistamine is also available in cream form as another option.
2. Hydrocortisone cream
Available from a pharmacist, hydrocortisone cream is a mild steroid cream that helps to reduce skin inflammation and itching. It can be very helpful in quickly reducing the symptoms of a sun rash.
3. Cold compress
Putting cold compresses on the affected area of skin can soothe and cool any sore area. Use flannels or towels soaked in cold water, or ice wrapped in a towel. Never put ice directly onto the skin as this can further damage it.
4. Protective gauze
If the rash is severe and blisters have occurred, covering these with gauze helps to protect them and keep them clean.
5. Desensitisation treatment
Although it is not widely available, desensitisation is a longer-term type of treatment which aims to treat the skin with courses of UV light to make it less sensitive. This is usually commenced by a specialist rather than a GP.
Extreme cases of sun rash can be treated with drugs that suppress the immune response but this is rarely prescribed and is reserved for the most severe reactions that do not respond to any other type of treatment.
When should you see a doctor?
If you experience a skin rash after being in the sun (that is not simple sunburn or a sweat rash) then ask your doctor for advice as other conditions such as lupus or contact dermatitis can also cause this problem.
If the rash is painful, badly blistered, widespread or there is a high temperature then seek medical attention. If you have never had a significant sun rash before and suddenly develop one, this should also be medically assessed.
Sun rash prevention tips
To minimise the risk of sun rash, consider the following:
✔️ Wear a sunscreen with a strong SPF of at least factor 30 before going out into the sun and reapply every two hours (sooner after swimming or if you sweat a lot).
✔️ Use a sunblock on your lips.
✔️ Wear sunglasses with ultraviolet light protection.
✔️ Wear loose dark clothing that covers as much skin as possible, and a wide brimmed hat. Carry a parasol too if it helps.
✔️ Try to go out in sunshine where your shadow is shorter than you are. This is typically between the hours of 10am and 2pm when the sun is at its most intense. If you need to do so, stay in the shade as much as possible.
✔️ Remember that if you are taking certain medications such as antibiotics this can trigger a skin reaction when it is exposed to sunlight. If you take medication regularly and spend a lot of time outdoors, check with your GP if you need to take any extra precautions to avoid sun exposure.
Last updated: 29-04-2021
You Might Also Like