Polymorphous light eruption (PLE) is a common skin rash that occurs due to sunlight exposure. PLE causes small bumps or raised plaques on the skin.

In the northern hemisphere, people who are prone to PLE often experience this condition in spring, when light levels begin to increase and people start wearing clothes for warmer weather.

The rash typically lasts only 2–3 days, but some people may continue having symptoms throughout summer.

Read on to learn more about PLE, including the symptoms, causes, and treatments.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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PLE is a skin rash that occurs in response to sunlight.

People with the condition usually experience symptoms at the same time of year, often when the skin first becomes exposed to sunlight after being covered up during winter. It is rare for people who get sunlight exposure year-round to have PLE.

PLE symptoms typically appear around 2 hours after sun exposure and last for several days before improving on their own. Some people may experience symptoms for longer than this, potentially all summer if they continue getting sun exposure, but this is uncommon.

Some people with PLE may find they react to even small exposures to sunlight, while others develop PLE only after a certain amount of time in the sun or as a result of repeated exposures.

PLE commonly affects people for many years, but most people’s symptoms improve or disappear over time.

Several types of PLE exist, each with slightly different symptoms.

The papular type is the most common. It causes small, raised bumps measuring around 2–5 millimeters across. Sometimes, these papules appear in a dense formation, making the rash look similar to eczema or prickly heat.

The other types are:

  • eczematous, which causes dry patches and plaques
  • papulovesicular, which causes small blisters
  • urticarial, which causes hives
  • erythema multiforme-like, which causes a rash of concentric circles

When the condition first appears, the most common symptoms include:

  • burning
  • itchiness
  • redness, in lighter skin tones

The rash will then appear on parts of the body that have had sun exposure, such as the:

  • backs of the hands
  • tops of the feet
  • V of the neck
  • forearms
  • lower legs

Some people also experience additional symptoms around 4 hours after sun exposure, such as:

These additional symptoms typically last for only 1–2 hours. A PLE rash does not usually leave scars or marks.

Researchers are not sure what causes PLE, but they believe it may occur due to a reaction by the immune system.

Usually, UV radiation suppresses the immune system, lowering inflammation. It is possible that people with PLE have some resistance to this UV-induced immunosuppression, which could result in skin inflammation, a 2022 review of research suggests.

There may also be a link with estrogen, according to the 2022 review. This hormone may prevent UV radiation from suppressing the skin’s immune responses. This may explain why females are much more likely to develop PLE than males, as they have more estrogen.

In up to 50% of cases, people with PLE have family members who also have the condition. This may suggest a genetic component, but researchers have not proven this.

A PLE rash can look similar to other skin rashes, so it is important to get a diagnosis from a doctor.

To diagnose PLE, a doctor will ask questions about a person’s symptoms, such as when they appear and what the rash feels like. They will also perform a physical examination of the skin.

If the symptoms have a clear connection to sun exposure, the doctor may base a diagnosis on this. If they are not sure, they may suggest a skin biopsy.

The doctor will diagnose PLE if a skin biopsy shows:

  • swelling caused by excess fluid in the upper part of the dermis, which is the middle layer of skin
  • the presence of cells from the immune system, including lymphocytes, dendritic cells, and T-cells
  • the formation of small blisters, or vesicles

A doctor may also consider phototesting, which involves exposing the skin to UV light to see if the skin reacts. However, this test can lead to false negatives.

PLE can look similar to other rashes, such as the rash that occurs in people with lupus erythematosus. If there is still doubt about the cause of the symptoms, a doctor may recommend tests to rule out other explanations.

There is no cure for PLE, but the condition often gets better on its own in a few days. If the symptoms do not improve or are severe, a doctor may prescribe:

  • Topical creams: A mild to moderate topical corticosteroid cream may help reduce inflammation. Another option is topical calcipotriol, which is a vitamin D derivative people can use before sun exposure.
  • Phototherapy: This involves controlled exposure to sunlight or artificial UV light under the direction of a dermatologist. Repeated and gradual exposure to the sun may reduce sensitivity. Doctors may use UVA or UVB light.
  • Oral corticosteroids: This stronger form of steroid medication reduces itching and speeds healing in severe cases of PLE.
  • Afamelotonide: This medication stimulates the production of a type of melanin in the skin, resulting in a tan. This can help protect the skin from UV light and reduce sensitivity to it.
  • Antimalarial medications: These medications may help with PLE if other options do not work.
  • Immunosuppressants: Doctors may use these in severe cases of PLE to suppress the immune response.

Because people get vitamin D from the sun, people with PLE can be more at risk for vitamin D deficiency. A doctor may suggest taking a vitamin D supplement instead.

A 2014 study suggests that nutrition may also play a role in how sensitive a person’s skin is to sun exposure. The researchers gave participants a supplement that contained:

  • beta carotene, which is an antioxidant present in many plants, particularly yellow, orange, and red fruits and vegetables
  • lycopene, which is an antioxidant present in red fruits and vegetables
  • Lactobacillus johnsonii, which is a type of probiotic

After 12 weeks, the participants taking the supplement had less severe symptoms than those who did not take it. People may wish to try this approach at home by eating more fresh produce that is yellow, orange, or red.

However, this study was small. The role of diet in treating PLE requires more research.

If PLE symptoms are mild, people may be able to manage the condition at home. This could involve:

  • staying out of the sun when it is most intense, between 10 a.m. and 4 p. m.
  • applying a mineral sunscreen with an SPF of 50 or above 15–30 minutes before going outside
  • reapplying sunscreen every 2 hours and after getting the skin wet

When outside, try to wear lightweight clothes that cover the skin, such as loose long-sleeved tops or dresses. Wear a hat with a brim and large sunglasses to protect the face and shoes that cover the feet.

It is not always possible to completely prevent PLE in people who are prone to it. Yet they can take some steps to reduce the symptoms, such as:

  • Get gradual sun exposure: If PLE often occurs in spring, try to gradually let the skin become used to sunlight before transitioning into summer clothes. This may involve exposing the arms or legs for short periods of time at first, then gradually lengthening the time. Wear SPF while doing this.
  • Avoid sensitizing products: Some topical products can increase the skin’s sensitivity to UV light. This includes products containing retinoids and acids, such as beta hydroxy acids and alpha hydroxy acids.
  • Check medications: Some medications can increase sensitivity to the sun as a side effect. Check the label to see if photosensitivity is a potential side effect. If the drug could be making PLE worse, discuss this with a doctor.

If a person develops a rash suddenly, they should speak with a doctor for a diagnosis. PLE can look like other skin conditions, some of which require prompt treatment.

PLE is a rash that develops in response to sunlight exposure. It typically comes back each year when a person begins to have more sun on their skin. The symptoms are usually self-limiting and go away after a few days.

Gradually exposing the skin to the sun, wearing adequate sun protection, and avoiding substances that increase photosensitivity may help prevent PLE or reduce the symptoms. If the rash does not go away, a doctor may prescribe topical creams or medications to manage it.