Prickly heat – how to prevent and treat.

Posted on Sunday, April 22nd, 2018

Courtesy of The Times:


Summer is coming and with it a scourge of my youth that has blighted many a holiday abroad. Indeed during the hottest summers (1976 was particularly bad) I even developed prickly heat at home. I am far from alone — as many as one in five people in the UK suffer from the sun-induced skin rash at some stage. So what is the best way to tackle it?

Prickly heat is an old-fashioned name for any itchy rash that develops in hot, humid or sunny conditions, such as those most of the UK is experiencing today. Herein lies the problem. The term is used to describe everything from sweat rash to an allergy to sunscreen, which goes a long way to explaining why so few victims find an effective remedy. What works for sweat rash won’t help allergies, and vice versa.

In practice, most cases of prickly heat have nothing to do with heat, sweat or allergies, but are caused by sensitivity to the UVA portion of sunlight — the highly penetrative fraction that can travel through clouds, glass, water and even some thin clothing. Doctors call it polymorphic light eruption (PLE) and the sensitivity is more common in women and typically first appears during childhood or early adulthood.

The classic symptoms of PLE include an itchy, red rash that develops two to three days into your holiday (or during a sunny spell at home). It is normally symmetrical, with commonly affected sites including the chest, tops of the feet and upper arms. It is unusual to develop it on areas more used to the sun, such as the face and backs of the hands.

The key to preventing prickly heat is to reduce exposure to UVA by using a decent sunscreen. These are rated in two ways. The sun protection factor (SPF) is a measure of how much protection they give against sunburn-causing UVB, while the star rating is a measure of the ability to block UVA rays, which cause prickly heat. If you are a regular sufferer go for a minimum SPF 20 (30 o more is better) and five stars, and reapply every two hours (UVA filters break down quickly).

Using the wrong type of lotion will make matters worse. We can all feel UVB-induced sunburn but have no idea what sort of dose of UVA our skin has received. So a high-SPF, low-UVA star-rated lotion (as most older lotions were) just encourages you to spend longer in the sun and makes matters worse — which is why so many prickly heat sufferers mistakenly believe they have an “allergy” to sunscreen.

UVA is highly penetrative so use the sunscreen even on cloudy days and in the pool, and try to avoid direct sunlight between 11am and 3pm when strength of UVA radiation is up to ten times higher than earlier in the morning or later in the afternoon.

Some dermatologists advocate beta-carotene supplements because they are thought to boost the skin’s natural defences to UVA (although the science is shaky); 10-15mg daily from a week before flying until the end of your holiday is a typical recommendation.

Last, avoid using a sunbed to give you a base tan before you go. Most sunbeds deliver much higher doses of UVA than natural sunlight and while a prolonged course can help to prevent prickly heat by desensitising your skin, a few sessions will have the opposite effect and make an attack more likely.

After more than 20 years of suffering I haven’t had an episode of prickly heat since following this regimen and it has worked for a lot of my friends and relatives. But PLE tends to settle with age and mine may have resolved spontaneously, so I am keen to hear your experiences if you give it a try this summer.

If you do develop prickly heat:

■ Avoid any sunlight on the affected area for at least 72 hours — and that includes sitting under a shade on a beach where reflected UV rays can still reach you. Cover up.

■ Antihistamine tablets are said to help but they never worked for me; the best bet is to apply a topical steroid cream twice daily to the itchy area. It will take 24 hours to have any effect, so persevere. You can buy 1% hydrocortisone cream over the counter, but stronger prescription-only creams are likely to work better.


2 Responses to “Prickly heat – how to prevent and treat.”

  1. Belinda says:

    Hi Dr Porter

    Firstly, I would like to thank you for such an interesting read. I have never experienced any sun related rashes until I went to the Canaries last year. I developed what I believe to be extreme prickly heat or some kind of PLE; my GP was unsure as to what it was or the specific cause. All I know for certain is that it was incredibly itchy, hot and later developed in to large blisters which took around two weeks to fully heal after being treated with high dose antihistamines, steroids and creams. I have experienced a similar reaction following the bank holiday hot weather although not to the same extent as before. I’m due to go back to the canaries in august and am becoming more and more anxious about having another outbreak. I’ve been reading about preventative measures such as taking vitamin c, beta carotene, vitamin B6 and vitamin e, alongside regular antihistamines before departure. I have also read that using an antibacterial soap before applying a uva protective sunscreen such as Ladival can be helpful. While I understand that you can’t reply, diagnose, or advise on an individual that you haven’t personally reviewed or assessed, I was just wondering if you had any experience or opinions around the use of vitamins prior to departure to a warmer climate, and if you could offer any thoughts around taking higher doses or vitamin c, beta carotene, vitamin b6 and vitamin e. I’m planning on seeing my own GP prior to my departure but I’m not sure if they will be able to advise (based on my own previous experience) of suitable doses or any implications around taking higher doses of these vitamins.

    If you do have the time to reply, your thoughts around this would be very much appreciated.

    Kind regards


    • Dr. Mark Porter says:

      Sounds like nasty PLE. I am assuming you are not any medication that could be photosensitising you.
      My only experience is with the beta-carotene mentioned above. Generally I find anti-histamines disappointing.
      Good luck on holiday

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