Polymorphous light eruption (PMLE) is an allergic reaction to sunlight or other sources of ultraviolet (UV) light. It usually takes the form of an irritated rash that comes hours to days after exposure to direct sunlight.

It’s the most common skin condition caused by sunlight. A study across Europe found that PMLE affects as much as 18 percent of the population there.

It’s also called polymorphic light eruption and prurigo aestivalis.

PMLE is generally treatable with both home remedies and medical interventions.

Read on to learn more about how PMLE might affect you and what you can do about it.

Symptoms of PMLE usually begin within a few hours to days after sunlight exposure, typically in the spring or early summer. An itchy rash will appear on areas that were newly exposed to the light, including:

  • décolletage (low neckline)
  • chest
  • forearms
  • backs of your hands
  • lower legs
  • feet

The rash usually doesn’t affect the face. While the rash varies from person to person, the particular rash you get will typically be similar every time it happens.

If you avoid UV light, your rash will heal on its own in a few days to weeks. It won’t leave any scarring.

It’s not as common, but you might have additional symptoms, like:

Polymorphic means “many forms,” and PMLE can look different for different people. Below are some examples of what PMLE can look like.

The exact cause of PMLE isn’t known, but genetics are thought to play a role. Experts have suggested it may also be at least partly associated with:

While the causes of PMLE are still under investigation, the rash is brought on by UV light.

It’s important to note that, while UVA exposure is the typical cause, the rash can be a result of UVA or UVB exposure. This means that glass windows won’t provide enough protection from the sun to prevent a PMLE reaction.

Is it contagious?

PMLE is not contagious. You can’t catch it from someone else who has it, and if you have it, you can’t pass it to others.

Anyone can have PMLE, but it’s more common for people with lighter color skin, particularly Fitzpatrick skin type 1.

PMLE is about four times more common in women than in men. You might start feeling the symptoms at any age, but it typically begins in ages 20 to 40.

It also occurs more frequently in places that are at higher altitudes and in more temperate climates.

There aren’t any severe physical complications strongly associated with PMLE, but a severe case of the condition may lead to:

If you have PMLE and you find that it’s affecting your well-being, a healthcare professional can advise you on appropriate strategies to manage these feelings.

The effect is not fully understood, but PMLE can undergo a process called hardening. This means that, as you’re exposed to UV light, your skin can build up a UV tolerance.

Your first eruption of the year may be the most severe, with following eruptions progressively subtler.

Gradual hardening is one form of treating PMLE. This can be done through careful and measured exposure to sunlight, or it can be achieved through the use of phototherapy.

Dermatologists can expose you to UV light a few times per week before the sun becomes strong in the spring to help avoid severe PMLE. This should only be done by a professional. This typically has to be repeated after every winter.

After the rash has already appeared, a doctor may prescribe corticosteroids to help alleviate itchiness or burning.

Other medications that might be used to treat PMLE include:

If you have an unexplained rash, you should make an appointment with a primary care physician or dermatologist.

A rash can be a symptom of many different conditions. If you have a rash in addition to other symptoms that are more serious, you may need emergency care. If in doubt, call a doctor.

PMLE is usually diagnosed based on its symptoms, primarily the appearance of the rash when it occurs, where it’s located, and how quickly it heals.

A skin biopsy might be taken in order to confirm the diagnosis, but this is not always necessary. Blood tests might also be used to rule out other conditions.

In some cases, a doctor might expose a small part of your skin to UV light in order to confirm PMLE.

To reduce the effects of PMLE, the American Academy of Dermatology (AAD) recommends seeking shade and applying sunscreen. If you can, avoid the sun when it’s at its strongest during the middle of the day.

Experts recommend using sunscreen that’s SPF 50, broad spectrum (meaning it blocks both UVA and UVB rays), and water-resistant. You should reapply every 2 hours.

Additionally, the AAD suggests covering your skin from direct sun exposure. There are many clothing choices that can help you do this, such as:

  • dense fabrics
  • dark or bright colors
  • long-sleeve shirts and pants
  • wraparound sunglasses with UV protection
  • wide-brimmed hats that cover your head, neck, and ears
  • shoes that fully cover your feet

Polymorphous light eruption is a condition that causes your skin to react to light, usually UV light. Most UV light you are exposed to comes from the sun.

When your skin is exposed to sunlight, a rash will form within a few hours or days. Without additional exposure it will heal on its own.

Women between 20 and 40 with pale skin are the most affected, but anyone can have PMLE. It’s most pronounced during the spring and early summer.

Your skin can build up a tolerance to UV light throughout the summer, but this will go away during the winter.

The best way to address PMLE is to avoid direct sun during the strongest parts of the day, wear appropriate sunscreen, and wear clothing that covers your skin. These are good practices for everyone, with or without PMLE.