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Dangers of the Sun : Polymorphic Light Eruption

As many as 15% of people in the United Kingdom may be affected by a condition called Polymorphic Light Eruption (PLE), which is an abnormal reaction to sunlight, a leading Dermatology clinician has advised Canopies UK.

The dangers of the sun are well-known but aside from the risk of skin cancer and melanoma, people may also suffer from other conditions such as PLE, which is an itchy rash occurring after sun exposure. The British Association of Dermatologists charity estimates on their website that as much as 10% of the UK population may be affected by the condition, which can mean that some people have to be more controlled in the amount of time they spend in the sun compared to others.

But Dr Sally Ibbotson, a Clinical Senior Lecturer in Photobiology at the University of Dundee and Ninewells Hospital and Medical School, has reason to believe that this figure may actually be higher: “In the UK, the proportion of patients with polymorphic light eruption is of the order of 15% although I suspect that this is an under-estimate as many people with milder forms of disease think this is sunburn, a reaction to sunscreen or heat and do not present to the doctor.”

Science basics: The Sun

Whilst for many the sun is a source of enjoyment, most are unaware of just how much damage they can be doing to their skin. The sun produces vast amounts of energy and light, but humans only see a very small part of that electromagnetic spectrum, known as ‘visible light’. Outside of this part of the spectrum, harmful rays that cannot be seen by humans can cause damage to our skin and lead to medical issues further down the line.

Ultraviolet radiation (light) is the main culprit, although much of it is absorbed by the ozone layer in the atmosphere. Dr Ibbotson clarifies: “UV light is the most damaging part of the electromagnetic spectrum in terms of the risk of burning or skin cancer. Visible light can be problematic in patients who have some photosensitivity conditions in which abnormal visible light sensitivity is part of the disorder.”

Light can affect people in different ways. When our skin is exposed to sunlight, our body produces a pigment called melanin, which absorbs UV light. People with fairer skin, of a lighter complexion, or those with red or blonde hair, usually have lower levels of this pigment meaning they are at more risk from burning, but even those with lots of melanin can still  burn regardless of race or gender depending on the amount and type of sun exposure. This means that it is important to ensure that an appropriate sunscreen with high protection factor is applied at regular intervals.

“People with fairer skin have less constitutional melanin protection from sun exposure and therefore are most at risk of burning, and of skin cancer in the longer term,” explains Dr Ibbotson. “The photosensitive condition, polymorphic light eruption, is commoner in northern latitudes although we do also see photosensitive conditions in patients with darker skins.”

Polymorphic Light Eruption: What is it and how does the sun cause it?

Following sun exposure some people may find that their skin starts to develop an abnormal reaction. This can range from an itchy red rash to blisters forming on the skin. It usually takes between a few hours to days for this to be visible, however NetDoctor advises that in some cases symptoms can appear in just 15 minutes.

The exact cause of PLE and why it appears after sun exposure is not fully known, however, restricting exposure to sunlight should mean that the rash disappears after a few days, with no noticeable consequences such as scarring.

“The hypothesis is that the sunlight in some way alters an endogenous protein or chemical in the skin changing it so that this is then antigenic and a delayed cell-mediated hypersensitivity reaction occurs resulting in the rash of PLE,” advises Dr Ibbotson. “In people who do not have PLE, ultraviolet light causes dampening down of the skin’s immune system as a normal phenomenon. It seems that in PLE, this dampening down procedure of ultraviolet radiation is impaired and this may explain, at least in part, why the rash of PLE develops.”

How can I avoid this?

There are many simple ways of restricting and preventing PLE without feeling like you are not able to enjoy the sun as much as everyone else. This includes avoiding direct exposure to the sun during the hottest part of the day (between 11am and 3pm), wearing clothes that protect your skin from the sun and applying a high factor sunscreen (SPF >30). Having a shaded area in your garden can help, as it means you will be able to avoid long exposure to the sun while still being able to enjoy your surroundings and the warm weather.

Dr Ibbotson is particularly keen to ensure that people do not feel like they have to compromise their lifestyle significantly as a result of being diagnosed from PLE.

“We don’t suggest that people with photosensitivity conditions avoid sun exposure and certainly we are not wanting to compromise lifestyle.  However, we would suggest sensible precautions.”

In fact, gradual exposure to sunlight can help to increase the time before any sort of reaction takes place: “In Polymorphic Light Eruption patients may in fact be able to induce hardening (toughening up of their skin) by exposing themselves to lower levels of sunlight than would be required to trigger the rash and this can raise the threshold for provoking the rash.  Therefore we do not advocate that they spoil their lifestyles by avoiding the sun altogether,” added Dr Ibbotson.

I suffer from polymorphic light eruption – what should I do?

A cautious, gradual introduction can help the skin adapt to sensible sunlight exposure. Ensure that appropriate clothing and high factor sunscreens are used and prolonged exposure to the sun should be avoided. Ensure that parasols are provided which you can escape under, and buy a big floppy hat to avoid exposure to your head. Dr Ibbotson advises that a change in attitude away from “sunseeking behaviour” is also important in addition to any physical adjustments.

“In general we encourage people to modify their behaviour, avoid direct sun exposure on sunny days between 11.00 and 3.00, to seek out the shade, use wide brimmed hats and to cover up with clothing with tight weave and use high factor sunscreens such as SPF 30-50.”

“Use of gazebos and sun shelters can be very helpful.  Be aware that polymorphic light eruption can be triggered with light coming through window glass (UVB light is not transmitted through window glass but UVA and visible light are).”


What is the future for PLE sufferers?

“PLE can spontaneously resolve.  We have no therapy at present to switch off i.e. cure the condition and this is compounded by the fact that we do not fully understand the pathogenesis of this disorder.  Further research is required to clarify this,” explains Dr Ibbotson.

“Studies are being undertaken to investigate the underlying pathogenesis of polymorphic light eruption and to explore the potential use of new treatments and preventions.”

Phototherapy treatment can help reduce sensitivity

One of the areas that Dr Ibbotson has invested a lot of time both in terms of clinical practice and research,  is phototherapy, which can help to harden the skin ahead of exposure to natural sunlight.

“Phototherapy for photosensitive conditions is commonly used to desensitise (harden) the skin and this is particularly the case in PLE.  After a treatment course, if the patient does not have some natural sunlight exposure then protection from the phototherapy course would be lost within a period of four to six weeks and the patient’s usual photosensitivity will return.  This is why it is important that we time phototherapy for desensitisation so that it is carried out during a season where natural sunlight top-up is possible or prior to the patient going abroad.”

When asked about future improvements to phototherapy treatments, particularly at the University of Dundee, Dr Ibbotson added: “In the Photobiology Unit we have an interest in the development of new forms of light therapy and were the first centre in the UK to introduce narrowband UVB and UVA1 phototherapies.”

“We are also looking at innovative ways to deliver light therapies and have a home phototherapy programme within the unit and are also now undertaking a self-administrated phototherapy regime where patients are more in control of their own treatment.”

“We have interest in other forms of light-related therapies including photodynamic therapy (PDT) for certain types of skin cancer and are now using portable light sources for home-based PDT and have adopted the use of daylight for PDT.  We have a range of lasers in the department for a variety of clinical indications and we are also the only centre in the UK to have Grenz Ray therapy for certain recalcitrant skin disorders.”

Please note: The information provided is provided for general purposes and should not be a substitute for actual medical advice. In the event that you have concerns, you should contact your GP or a medical professional immediately, who will be able to advise further. Canopies UK is not responsible or liable for any form of damages relating to the use or misuse of this article based on the information provided or implied. If you have any urgent concerns, please call NHS Direct on 111.

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