DR PHILIPPA KAYE: What’s causing that mysterious summer rash – and how you can get rid of it

Like many people, I’ve recently spent a fair few evenings freezing while alfresco dining or dodging the rain at garden parties. 

Now we’re set for a heatwave. Without wanting to sound like a killjoy, I am beginning to worry about the effect it’ll have on the nation’s skin.

We all know about avoiding sunburn (and will have probably suffered a painful reminder at some point about just why we should), but problems can reach far beyond forgetting to apply enough suntan lotion.

Up to one in four of the population suffers a diagnosable skin condition, and many of these are linked to sun exposure. 

Indeed, in the summer months I see a raft of rashes and other skin complaints in my surgery that are far less common during the winter.

Alongside heat, which causes problems in itself, the sun emits invisible ultraviolet (UV) radiation. 

We all know about avoiding sunburn (and will have probably suffered a painful reminder at some point about just why we should), but problems can reach far beyond forgetting to apply enough suntan lotion. Up to one in four of the population suffers a diagnosable skin condition, and many of these are linked to sun exposure

The type that causes sunburn is called UVB, but in the case of skin ageing it’s another type – UVA – which penetrates the skin more deeply, that’s the culprit. But both are linked to skin cancer, as well as other rashes.

That’s why, if you’re going to be exposed to the sun for any length of time, it’s important to apply a sunscreen that has protection against both UVA and UVB. 

Aim for a high sun protection factor (SPF) of at least 30, as well as a high star rating – a measure of how good it is at blocking UVA rays – of at least four out of five.

It’s important to note that UVA rays, unlike UVB ones, can penetrate glass, so if you have sensitive skin you might find that just sitting by a window on a sunny day is enough to trigger an outbreak. 

However, help is at hand. There are steps that can be taken to avoid, or at least minimise, problems.



If you’re suffering from crops of itchy, red or pink raised spots on the arms, upper chest or lower legs – parts of the body that are usually covered up but have been exposed to the sun – it could be what’s known as polymorphic light eruption.

The spots can join up into sheets or red, inflamed skin, or more rarely take the form of a ring, like a bull’s-eye. 

Some people suffer blisters that turn into larger, scaly patches that look like eczema.

Polymorphic light eruption affects between one in ten and one in 20 people, and women account for roughly three-quarters of all sufferers. 

It can run in families, and typically it’s seen in those with fair skin, but people with darker skin can get it too.

It’s thought to be due to an immune-system reaction, and the first episode usually happens between the ages of 20 and 40.

The rash may be a rare occurrence or may happen every time the skin is exposed to sunlight, and ranges from mild to severe.

Sometimes as little as 30 minutes of sun exposure is enough to cause the problem, and it can even develop through thin clothing or if you’re sitting near a window.


First thing – get out of the sun and cover up. If further exposure is avoided, the rash can settle in a few days and will disappear in a matter of weeks. 

But if it gets more sun it can get far worse, and even when the rash has gone it can come back if the skin is exposed again.

There’s no cure, but sunscreens – a SPF 30 or more with a good UVA star rating – and staying covered up and in the shade will help. 

If you’ve already erupted, a GP can prescribe a strong steroid cream. 

It can help to gradually expose the skin to the sun earlier in the year, but people with a bad case of polymorphic light eruption might be recommended light therapy in hospital in the spring.

This involves exposing the skin to UV light, emitted by a machine, over four to six weeks to build up resistance. The effects are lost in the winter, so has to be repeated every year.

As sufferers have to avoid the sun, Vitamin D deficiency can be a problem, so speak to your GP or pharmacist about a supplement.



Another common rash is prickly heat, also known as heat rash or miliaria, which can look strikingly similar to polymorphic light eruption. 

What’s the difference… 

…between scurvy and rickets? 

Both are caused by a serious deficiency in essential nutrients.

Scurvy develops when there isn’t enough Vitamin C – found in fruits and vegetables – in the diet for at least three months, which is why it is historically associated with sailors on long sea journeys. 

Sufferers may feel weak, come out in spots and have severe joint and leg pain. 

Rickets affects bone growth, mainly affecting children who do not get enough calcium and Vitamin D in their diet.

Both are treated with large amounts of the nutrients via diet or supplements.

It also manifests in clusters of itchy or stinging vivid red bumps.

The spots can join up into sheets and form blisters but, unlike the UV-triggered condition, this occurs in areas that are covered, usually the chest and back and is the result of blocked sweat ducts. 

This traps sweat under the skin, causing inflammation.

Often hot, humid weather can be a trigger. Three in ten adults suffer with the condition, and being overweight or prone to excessive sweating increases the risk.

Prickly heat is also seen in babies, as their sweat glands are not fully developed and are therefore prone to inflammation.


The rash – even in severe-looking cases – subsides without treatment within a few hours in a cool environment, and disappears without trace in a day or two. It’s important that the sufferer avoids hot environments.

To avoid getting the rash, keep cool – if you can’t find a nice air-conditioned room, an electric fan can be a lifesaver – and wear loose cotton clothing that allows the skin to breathe. 

Calamine lotion or an over-the-counter hydrocortisone cream will help itching, but speak to your pharmacist first.



Phyto means plant, photo means sunlight and dermatitis means inflammation of the skin. 

Phytophotodermatitis occurs when compounds in certain plants react with UVA light, causing damage when it touches skin.

The rash happens wherever the skin has been exposed, and is itchy, burning red, or even bruise-like. The skin can also blister.

Gardeners can get it on their hands – giant hogweed is a common cause, as is rhubarb.

Citrus fruits can also trigger the reaction, which is why we often see it round the mouths of children who have been eating ice lollies made with real limes or lemons.


Over-the-counter hydrocortisone cream or calamine lotion will soothe itching. If it doesn’t subside within a few days, your GP may prescribe a stronger steroid. And while gardening, wear long sleeves and trousers.



Like prickly heat, this isn’t caused by sunlight but is the result of a fungal infection more commonly seen during hot, humid weather. 

The rash has a red, slightly raised, often ring-like appearance, which can be dry-looking or flaky. 

It can itch or even burn, and it typically appears high up on the inner thighs, in the crease of the leg, or on the groin, and is more common in men.

Jock itch is actually a fungal infection, similar to athlete’s foot, caused by a group of fungi called dermatophytes that normally live problem-free on the skin. 

Prolonged exposure to moisture – such not changing out of wet swimming gear – can cause the fungi to grow and lead to infection.


Showering or washing daily, drying off thoroughly and getting out of damp clothes quickly are the best forms of prevention.

For an active infection, there are a range of over-the-counter antifungal creams, powders or sprays. 

The affected area should be kept clean and dry and – this goes without saying – underwear changed daily.

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