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Jan 23, 2021

Is Polymorphic Light Eruption Genetic?

Polymorphic light eruption, by its very nature, comes in a wide variety of shapes and sizes. For some people, it's a mildly uncomfortable bumpy rash that occurs on newly-exposed skin at the first bright day of spring; for others, it’s a debilitating condition that blights summer, with blisters, hives and intense itching at the slightest hint of sunshine.

There’s no definite conclusion to the question of why some people get polymorphic light eruption (aka PMLE), and get it so severely, and some aren’t bothered by sunlight at all, but recent research has been looking at whether it’s an inherited condition as well as an environmental one.

The environmental/circumstantial factor is more obviously understandable: polymorphic light eruption tends to occur in light-skinned people, who live in places where their skin is covered up most of the year. It’s an extreme and abnormal reaction to UV light, the body’s immune response mechanism kicking in to protect itself against sunshine with a flood of histamine, that in turn triggers itchiness and inflammation. 

The factors that determine whether someone is more likely to experience PMLE seem to be:

  • Being female: women are more at risk than men
  • Being over 20 and under 40: adults are more likely to suffer than children
  • Having pale skin: lighter-skinned people are at higher risk than those with more melanated skin
  • Living somewhere with relatively cold and un-sunny weather in winter
  • Having a relative with PMLE

None of these factors is absolute: not every sufferer fits this demographic, and not everyone who ticks the boxes will experience photosensitivity, but it can be a useful generalisation when looking at who is more likely to be sensitive to sunlight.

However, the evidence is clear that there is indeed a genetic component to PMLE, with a statistically significant number of people having a family-member who also suffers from the condition. One study gives figures, concluding that “the prevalence of photosensitivity in first-degree relatives was 20.9% compared with a population prevalence of 13.6%, giving a relative risk of 1.5 and providing evidence of clustering within families.”

But while the evidence points to there being an inherited tendency to PMLE, it is likely to takes environmental circumstances to actually trigger an outbreak; hence the classic PMLE on the first bright and sunny day of summer situation, where someone who fits the bill in other ways (pale, inherited genetic predisposition) will experience an outbreak if they’ve gone out into the garden wearing a tee shirt for the first time that year!

Read our blog How Is Polymorphic Light Eruption Treated? For more detailed information about ways to look after skin prone to PMLE.

Our products do not contain sunscreens! Do not apply oils or oil-based balms like Skin Salvation to exposed areas of skin in bright sunlight, as the oils can make the skin more likely to burn.

Recommended products:

Balmonds Daily Moisturising Cream
with shea butter and calendula

Balmonds Cooling Cream
with shea, menthol, aloe vera & lavender

Important Note

If you require medical advice we recommend you always contact your healthcare professional.

If you or someone you are caring for seems very unwell, is getting worse or you think there's something seriously wrong, call for emergency services straight away. For general medical advice, please contact your healthcare professional, this article does not contain or replace medical advice.

Do not delay getting help if you're worried. Trust your instincts.

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