If you find yourself developing an itchy, red rash after spending time in the sun, you may not be alone. While many attribute these symptoms to prickly heat, a common sun allergy known as polymorphic light eruption (PLE) could actually be the cause. People taking medicines such as atorvastatin and naproxen should consider consulting their GP to discuss their symptoms.
Dr Mark Porter, an NHS GP with nearly 40 years of experience and MBE recipient for his services to medicine, recently responded to a member of the public who believed they had prickly heat and had been advised by friends to avoid sunscreen. Dr Porter explained, through a blog post on SAGA, that the symptoms are more consistent with PLE rather than prickly heat.
He described classic prickly heat (miliaria rubra) as being caused by blocked sweat glands and more common in hot, humid conditions rather than simply strong sunlight. In contrast, “Your story is more suggestive of another condition called polymorphic light eruption (PLE). It is often confused with prickly heat, which might explain why your friends' advice hasn’t helped and is probably exacerbating the problem.”
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PLE stems from a sensitivity to sunlight, particularly the UVA rays that penetrate through clouds, water, glass, and even some clothing, resulting in an itchy, red rash that appears anywhere from a few hours to several days after sun exposure. A typical case involves the rash developing on the second or third day of holiday in the sun.
Dr Porter noted that PLE usually appears symmetrically on both sides of the body, often affecting the chest, tops of the feet, and arms. Preventative measures focus on reducing UVA exposure, primarily through the use of a high-quality sunscreen - ideally SPF 50 with a five-star UVA rating, reapplied every two hours - and avoiding direct sunlight during peak hours between 11am and 3pm.
“In new cases, it’s worth checking whether recently started medications (such as some statins, doxycycline, thiazide diuretics, or naproxen) could be triggering photosensitivity and discussing the rash with a GP,” Dr Porter stressed.
He advised that certain medications might worsen or trigger PLE symptoms. These include some statins like atorvastatin, tetracycline antibiotics such as doxycycline, thiazide diuretics like bendroflumethiazide, and the anti-inflammatory drug naproxen. Patients who have recently begun taking these medications and develop a rash should consult their GP to assess if these drugs might be responsible.
Some dermatologists suggest beta-carotene supplements might help, though Dr Porter admits “the science is shaky.” If taken, the usual dosage would be around 15mg daily, commencing a week before exposure to the sun and continued throughout the sunny period.
PLE often first appears in early adulthood, particularly among women in their 20s and 30s, and it is unusual for the condition to develop later in life.
The NHS points out that the rash may occur anywhere on the body but often appears on areas not commonly exposed to the sun, such as the arms, legs or chest. A related rash known as juvenile spring eruption can appear on the ears, forming small, itchy blisters.
While certain medications might contribute to or worsen PLE, this is not definite. Anyone concerned about their symptoms should always seek advice from their doctor.