If heat rash is making life a living hell, read on for the experts' (and sufferers') advice on what causes prickly heat, how to get rid of heat rash and how to keep your cool with these remedies and treatments

I don't do well in hot weather. Prickly heat, heat rash or 'sweat rash' as it might be known (not to be confused with polymorphic light eruption or PLE  - see below, also known as sun allergy) has plagued me, on and off, for as long as I can remember. Being sensitive, I'm always on the lookout for the beginnings of rashes or reactions, but there's none I dread more than the early signs of heat rash - those little red spots that start to appear on my wrists and the folds of my forearms, which I know within hours will be right up to my shoulders. Sometimes it even starts at the top - the sides of my arms and on my chest - before appearing elsewhere. Nowhere is safe.

As a friend and fellow sufferer once said to me, "Once you look down and see it - you know that's it." It's spoiled many a holiday, or indeed many a sunny day that should be spent frolicking outdoors and soaking up the vitamin D  (responsibly, of course; SPF always included ). Itchy, sore and unsightly, it can make summer a living hell. But what causes it and is there any way to stop those spots from creeping up on us?

I asked the experts to find out once and for all how to prevent heat rash and how to get rid of prickly heat if it's already made an appearance...

What is prickly heat?

"Prickly heat, heat rash or sweat rash are all names used for a condition called miliaria," explains Dr Stefanie Williams, Dermatologist and Medical Director of Eudelo clinic. "It occurs when sweat ducts get obstructed, sweat leaks into the skin and the skin gets inflamed around that tiny leakage. A prickly rash appears with red, very itchy little bumps (papules)."

The sweat ducts are blocked either by excessive sweating or by an overgrowth of bacteria which normally lives on our skin, Cosmetic Dermatologist  Dr Sam Bunting tells me. "[This] leads to a sticky byproduct blocking up the delicate sweat ducts, trapping sweat under the skin. It's exacerbated if sweat is trapped and can't escape."

MORE GLOSS: The best sun creams for sensitive skin

Who suffers from prickly heat?

"It is very common (up to 30 per cent of people may develop this under certain conditions) and is most common in hot, humid climates," says Dr Williams. "Younger children are particularly at risk. Typical body areas are skin folds (or on the back if a patient is bed-bound). The risk of getting it can also be increased if you use heavy, occluding skincare.

“However, sometimes when people speak about a sweat rash, they might possibly mean a fungal infection in skin-on-skin areas such as the groins or under the breasts. The medical term for this is Intertrigo and it’s a common fungal yeast infection that occurs between the folds of your skin as a result of humidity, friction and a lack of ventilation. It usually shows up as a red, itchy rash on skin folds.”

You don’t have to have a history of prickly heat to get it, either - it can happen at any time if you’re in the right (or should I say wrong) conditions.

It's worth noting, though, that many people think they're suffering from heat rash when in fact they are reacting to sun cream - it took me years to realise the extra-bad itchy rashes I was experiencing on holidays were from the bottles of sun cream I'd been slathering on all week and the fragrances and chemical sun filters in them. So do check that this isn't the case first ( see my guide to SPF for sensitive skin here ).

Either way, I'd recommend a fragrance-free mineral SPF to minimise irritation if you're prone to sweat rash - and ideally a once a day, a non-comedogenic formula like Ultrasun, £19, so you're not contributing to the root cause with top-ups throughout the day.

What is PLE or sun allergy?

Rashes are characteristically hard to diagnose, and though less likely than heat rash it could be that you’re suffering from a sun allergy or polymorphic light eruption (PLE).

Dr Williams explains: “They can look quite similar, but while heat rash occurs mostly in occluded skin areas prone to sweating, PLE occurs on skin that has been exposed to the sun recently (but traditionally might be covered with clothing, so isn’t ‘used’ to the sun).”

So what causes it? “PLE is a common form of a reaction to UV light that often occurs in young women in spring and summer (or at the start of a sunny holiday). The name ‘polymorphic’ refers to the fact that the rash can appear in many different shapes or forms, although in one person it usually looks the same every time it appears. The arms, the chest and lower legs/feet may be affected. The face is usually spared (as it tends to be more ‘hardened’ to sunlight). The commonest form of PLE presents as crops of itchy, 2–5 mm pinkish ‘bumps’. In some people, tiny blisters may occur. PLE persists for some days (or longer if the affected skin is exposed to more sunlight) before spontaneously resolving without scarring.”

Unless you can get your skin used to the sun slowly and gradually throughout the seasons, it’s likely you’ll suffer from it every year. Get The Gloss Editorial director Victoria Woodhall suffered with it in her teens and early 20s and found that as her skin got used to the sun over the years she grew out of it. With sun allergy it is a case of using steroid creams or oral steroids if it occurs, or preventing it by using specialised UV machines to ‘harden up’ the skin and prep it for exposure. “Most importantly, stay out of the sun, once you have it (until it’s fully gone),” says Dr Williams. “Antihistamines can help with the itch too.”

Victoria, who lived in Germany at the time was given high-strength calcium tablets by a German pharmacist (see below) which worked instantly.

MORE GLOSS: The ultimate guide to buying SPF for sensitive skin

How can you prevent prickly heat rash?

The million dollar question. Given that the cause is the body's natural response to the heat, it's very difficult to manage which is no doubt why it causes so much stress to so many people. The key thing here is to keep your cool; easier said than done in heat waves but essential to keep those little bumps at bay.

"Prevention includes, most importantly, avoiding sweating as much as possible. Even if you manage this for only a few hours per day (e.g. an air-conditioned office), this already helps," explains Dr Williams. "Also avoid over-dressing, occlusive clothes (wear breathable clothing e.g. light cotton) and friction/rubbing from clothes. Furthermore, you should avoid any irritation of the skin (e.g. excessive soap etc.)"

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It's of course a little harder to avoid hotter climes on holiday but there are ways to keep your skin as sweat-free as possible. "A dip in the pool or cool shower can stop sweating," explains Dr Bunting, "and avoid sticky skincare and sunscreens, which will have an occlusive effect on skin by trapping sweat." Check out our guide to preventing excessive sweating here, and my pick of the best sun creams for sensitive skin here  - pick your formula carefully and you might just avoid it.

Supplement-wise, try Nature's Way Nettle Leaf Capsules, £15.91 for both the treatment and prevention of prickly heat. "Nettle is commonly used because of its ability to inhibit the release of histamine which is responsible for the prickly heat rash. Additionally, nettle leaf extracts are powerful diuretics helping to eliminate the compounds that are responsible for the inflammation of the sweat glands," says Shabir Daya, pharmacist and founder of online pharmacy Victoria Health.

Another supplement to try is calcium tablets. Little-known in this country, this is a remedy suggested by pharmacists in Germany. GTG editorial director Victoria Woodhall can attest that it works. “I had no expectations at all, but it got rid of my sun allergy almost overnight,” she says. I took high-strength ‘fizzy’ tablets that I had to add to water once a day.”  

In fact, calcium is still very much offered in Germany as a remedy such as Calcium Sun 500 Direct Portion Sticks, £29.95 which has 500mg of calcium plus vitamin C, D3, E and beta-carotene. Says pharmacist and homeopath Margo Marrone, a 500mg dose twice a day is safe. Try Bio-Calcium D3 + K1 + K2 by Pharma Nord, £7.95 which has 500mg calcium per chewable tablet.

Dr Barbara Sturm, the Hollywood skin doctor, who hails from Germany, has included calcium in her new Sun Skin, £65, a supplement with anti-ageing benefits and “sun allergy protection, care of calcium and beta-carotene,” she states, proving it’s a medically endorsed remedy. Calcium is the primary ingredient, but the amount is not stated.

Some readers have suggested (see the comments below) that using an anti-bacterial Dettol soap to wash with has helped them to keep the rashes away - but what’s the expert view on using such a harsh detergent on sensitive skin? I asked Dr Williams. “In this particular case, it might have worked, as the soap reduced the bacterial overgrowth on the skin, which in some cases can be involved in the genesis of prickly heat. Everybody is different, but it wouldn’t be a treatment I would recommend routinely.”

Knowing my own sensitivities, I was nervous to try it myself, but found that using the sensitive version on a recent holiday to Malta proved helpful in at least minimising the rash (though I also had everything else I usually rely on so it's difficult to attribute too much credit to one soap). If your skin is otherwise robust aside from heat rash, then it’s certainly worth a try. I bought a pack of six from Amazon here.

How to get rid of prickly heat

So you’ve tried your best, but the rash has still appeared. What to do? Well if prevention is difficult, treatment is a pain when it comes to prickly heat - everyone has their own answers but ultimately, it’s hard to get rid of once the rash begins.

Prepare yourself and you shouldn't have to suffer for too long. Here are my top five tips for curing it once you've got it.

1. Do NOT scratch

2. Take antihistamines up to two weeks before you go on holiday (check with your doctor first - your GP can also prescribe some) or as soon as you start to develop the rash. Try also calcium tablets (above).

3. Shop for over-the-counter sprays and remedies (but with minimal ingredients - this is definitely a case of less is more. Fragrance has no place here). Dove 0% Cucumber Deo, £2, is an antiperspirant spray that's perfume-free and based on aluminium salt to reduce excess sweating and Eau Thermale Avene's Thermal Spring Water Spray, £9.75, is a great handbag essential for calming skin on the go.

4. "Leave the area as open and ‘ventilated’ as possible," advises Dr Williams, and try "cold water compresses and calamine lotion plus a light emollient (as calamine on its own can dry the skin and irritate a little)." I love  Care's Aqueous Calamine Cream, £2, which has fixed my heat rash every year I've had it - buy online or find in your local pharmacy.

5. Bathe it if needed in cool water. "If it's very itchy, try a colloidal oatmeal bath (try the  Aveeno Soothing Bath Treatment, £11.99, or make your own oat bath at home with this guide) and use a mild topical steroid for a few days," adds Dr Bunting.

6. Shabir suggests trying Lemon Balm Cream by Granary Herbs, £9, which can be applied three or four times a day. "When applied topically lemon balm helps to soothe itchy inflamed skin as well as being a good first aid cream useful for sores and cuts," says Shabir. " Thyme Out, £18, is another good option as the tonic helps to reduce inflammation and calm your skin. The formula is also very good at treating acne, eczema and sunburn, so it’s worth investing in for the whole family."

7. For sun allergy try the homoeopathic remedy Sol 30c, another treatment that worked for GTG’s Victoria Woodhall. Contact a homoeopath for advice or visit The Organic Pharmacy. Margo Marrone founder of the Organic says that Sol 30 and Urtica 30 (from nettles) are her go-to homeopathic remedies for treating sun allergy and prickly heat and they have worked on thousands of her customers.

MORE GLOSS: The best products for treating prickly heat