A sun rash is a skin reaction due to sun exposure. Although it may cause discomfort, a sun rash does not usually result in serious medical concerns.

The article below provides information on the types and causes of sun rash, as well as its symptoms. It also discusses a type of rash called polymorphic light eruption, how sun rash compares with sunburn, and treatments and prevention methods for sun rash.

According to the American Osteopathic College of Dermatology, a sun rash is the most common type of skin disease that occurs due to sunlight.

The sun can stimulate numerous types of rashes, 2021 research says. These include:

  • immune-mediated conditions, such as:
  • drug-induced photosensitivity as a result of the following types of medications:
  • photo contact dermatitis due to chemicals such as:
    • psoralens in plants, vegetables, and fruit
    • fragrances in cosmetics, such as sunscreen chemicals
    • dyes and disinfectants
  • metabolic disorders
  • genetic disorders

Causes

Most common sun-induced rashes, such as polymorphic light eruption, are worse upon initial exposure to the sun, such as in the spring. In the summer, the rash is not as severe.

While it may vary, most people with a sun rash develop the same pattern of symptoms each year.

Some people may also have photoallergic dermatitis. This condition involves an allergic skin reaction to a substance in combination with UV rays.

A common substance that may also cause photoallergic dermatitis and a rash is benzophenone-3, found in some sunscreens.

Read more about sunscreen allergy.

Symptoms of common sun rashes include:

  • a rash that appears where the skin was exposed to the sun
  • raised patches or bumps that itch or burn and are found in sun-exposed areas
  • less or no reaction on the face and other areas of the skin that are exposed to the sun most of the year

Typically, symptoms start about 2 hours after exposure to the sun.

The severity of a sun rash may vary. The initial symptoms include:

Some sun rashes cause small red dots, which are 2–5 mm in size. Rashes can appear differently on different skin tones. For example, on darker skin, the spots may appear white or gray.

Read more about signs of a rash on darker skin.

According to the Skin Cancer Foundation, polymorphic light eruption symptoms most often appear on areas of the body exposed to the sun, including:

  • chest
  • arms
  • legs

The skin bumps or lesions usually heal without any scarring. The condition may start at any time and can continue through a person’s life. In some cases, an individual may have a remission from the rash and not develop it for a few years.

Although symptoms may feel bothersome, a sun rash usually does not cause complications. In fact, 2022 research indicates that polymorphous light eruption is typically uncomplicated. But if the condition becomes severe, it can lead to:

Polymorphous light eruption is an immune-mediated rash that typically appears in the spring or summer. Experts suggest that occurs when a person has a delayed hypersensitivity reaction to an antigen expressed after exposure to sunlight or artificial sources of ultraviolet (UV) radiation.

The condition affects roughly 10–20% of the population. Usually, the sun rash causes small bumps that appear on the skin a few hours after exposure.

Risk factors

A sun rash can affect anyone, regardless of age or gender. However, certain risk factors make someone more likely to develop a sun rash.

Identified risk factors for polymorphous light eruption include:

  • Age: A sun rash often develops in women between ages 20 and 40.
  • Altitude: People who live at a high altitude above sea level are also at an increased risk of developing a sun rash.
  • Lighter skin: Individuals with lighter skin develop a sun rash more often than people with darker skin color.
  • Gender: Females are 2–3 times more likely to develop a sun rash than males.
  • Family history: A close blood relative with polymorphous light eruption appears to increase the risk. There is a family history association in about 50% of the people with the condition.

A sunburn and sun rash are both the result of exposure to the sun. However, symptoms and causes may differ. Sunburn occurs due to UV exposure that damages the skin’s outermost layer.

In contrast, a sun rash is a reaction by a person’s immune system to:

  • the sun
  • oral or topical medication
  • a chemical or plant

It can also result from a metabolic or genetic disorder.

People with lighter skin can detect sunburn more easily. Their skin may appear red and inflamed. In darker skin, however, it is harder to notice the subtle changes to the skin. The sunburn may feel tender to warm to touch.

Find out more about sunburn on darker skin.

Sunburn may cause the skin to peel as the burn heals, but this is less common with a sun rash.

Treatment may reduce discomfort and, in some cases, prevent the rash from spreading. Treatment options may include medications, home remedies, and topical creams.

According to 2021 research, treatment options include:

  • topical steroids for sun rash; depending on severity, doctors may prescribe a short course of oral steroids
  • local or systemic glucocorticoids to reduce inflammation
  • antihistamines for itch relief
  • over-the-counter anti-itch medications
  • a moisturizer, used when the skin heals to reduce irritation
  • a cool compresses, applied to decrease the burning sensation

The best way to prevent a sun rash is through suitable sun protection. According to the Skin Cancer Foundation, correct sun protection may help decrease the spread of a sun rash.

Consider the following steps to protect the skin:

  • using a broad-spectrum sunscreen with an SPF of 50
  • applying sunscreen every 2 hours to areas of uncovered skin
  • wearing sun protective clothing to block UV rays
  • avoiding sun exposure between 10 a.m. and 4 p.m., when the rays from the sun are most intense

A person can also take low dose oral steroids before exposure to the sun, experts suggest.

Another option to prevent rashes is phototherapy.

Phototherapy is a type of desensitization involving repeated exposures to sunlight. The repeated exposures help reduce the overreaction by the immune system to the sunlight, which may prevent future sun rashes.

In most cases, a sun rash does not require professional medical care. However, it is helpful to see a doctor in the following instances:

  • Severe hives or a rash develop.
  • The rash is very painful.
  • Signs of a skin infection develop, such as warmth to the touch, pain, and fever.
  • Swelling develops in the:
  • A person has difficulty breathing.

Polymorphic light eruption is a type of sun rash that occurs due to sun exposure. Research suggests hypersensitivity to the sun is the main possible cause.

The goal of treatment is to decrease discomfort and protect the skin from further damage. In most cases, a sun rash is not serious and does not cause complications.

To prevent a sun rash, a person should protect skin by:

  • using SPF 50 sunscreen
  • wearing protective clothing
  • applying sunscreen 2 hours prior to sun exposure
  • avoiding sun exposure between 10 a.m. and 4 p.m.