Sun Rash: Symptoms, Allergy, Treatment, Causes, and More

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Sun rash, also known as polymorphic light eruption (PLE), is a red, itchy rash that appears on the skin due to sunlight exposure. It is an autoimmune response that typically begins in the spring and ends by fall.

Sun rashes can appear on the skin after exposure to sunlight. It can take as little as 30 minutes of sun exposure to trigger the rash. The rash can develop within a few minutes to hours after exposure, and it typically resolves within 14 days without leaving a scar.

Sun rashes can appear in a variety of ways. The most common form is papular sun rash, which looks like small, red, smooth-topped bumps that are close together. These bumps can then form raised red patches called plaques. Plaques typically appear on the arms, legs, and chest. They can also include fluid-filled blistered areas called vesicles.

Other forms of sun rash include:

  • Erythema multiforme. Characterized by red, round patches that may be flat or raised.
  • Solar urticaria. A type of hives that is triggered by sunlight.
  • Actinic prurigo. A chronic rash that is characterized by small, red bumps and nodules.

Symptoms of a sun rash

Sun rashes are a common skin condition that can appear after exposure to sunlight. The rash usually goes away on its own if the skin is covered and not exposed to additional sunlight.

They are most common in females between the ages of 20 and 40. The symptoms of a sun rash can vary, but they often include:

  • Red, raised bumps or patches
  • Large blisters
  • Itching
  • Bruising
  • Eczema-like dryness

In most people, the skin becomes less sensitive to sunlight over time, which is known as hardening. This means that people who are exposed to sunlight all year round rarely develop sun rashes.

They often start in small areas, but the patches can expand during succeeding summers. Many people will have sun rash flares each summer. The amount of sunlight that a person can be exposed to before developing a sun rash varies from person to person.

What causes a sun rash?

A sun rash is caused by a combination of factors, including autoimmune conditions, UV radiation and genetics.

Autoimmune condition

Researchers believe that they are caused by an autoimmune response to sunlight. This means that the body’s immune system mistakenly attacks its own cells after being exposed to sunlight. The immune system normally suppresses its response to sunlight, but in people with sun rashes, this suppression is decreased. This allows the immune system to attack the skin cells, which leads to an inflammatory reaction.

Medically, sun rashes are described as a type 4 delayed hypersensitivity immunological reaction. This type of reaction occurs when the body’s immune system is exposed to an antigen, which is a foreign substance. The immune system then produces T cells, which are white blood cells that help the body fight infection. In people with sun rashes, the T cells do not function properly, which causes the immune system to attack the skin cells.

UV radiation

Sun rashes are a type of skin rash that is caused by an abnormal immune response to ultraviolet (UV) light. This response is delayed, meaning that it may not occur until hours or even days after exposure to UV light. The UV light triggers the release of certain chemicals in the skin, which can then cause an inflammatory reaction.

UVA radiation is the most common cause of sun rashes, accounting for 75% to 90% of cases. UVA radiation can penetrate the skin more deeply than UVB radiation, which is why it is more likely to cause sun rashes. UVA radiation can also come through windows, so it is possible to get a sun rash even if you are not directly exposed to the sun.

UVB radiation is the primary cause of sunburns, but it can also cause sun rashes. UVB radiation is more likely to cause a rash on the face and upper body, while UVA radiation is more likely to cause a rash on the lower body and arms.


People who are prone to sun rashes often have a genetic predisposition to the condition. This means that they are more likely to develop them than people who do not have this genetic predisposition. The genetic predisposition is combined with environmental factors, such as exposure to sunlight, to trigger the development of sun rashes.

A family history of sun rashes is found in 10% to 63% of related cases. This means that if you have a family member who has experienced them in the past, you are more likely to develop them yourself.

The exact mechanism by which the genetic predisposition to sun rashes works is not fully understood. However, it is thought that certain genes may make the skin more sensitive to sunlight. This can lead to an abnormal immune response to sunlight, which can cause the symptoms of sun rashes.

Risk factors

Risk factors are things that can increase the likelihood of developing a condition. However, having a risk factor does not mean that you will definitely develop the condition.

They are more likely to occur in people with certain risk factors, including:

  • Female gender: Women are more likely to develop these rashes than men.
  • Age: They are more common in people between the ages of 20 and 40.
  • Family history: If you have a family member with sun rashes, you are more likely to develop them yourself.
  • Temperate climate: People who live in temperate climates, such as the United States, are more likely to develop them than people who live in tropical climates.
  • Fitzpatrick skin type 1: People with Fitzpatrick skin type 1 have fair skin that is more sensitive to sunlight. They are more likely to develop them than people with other skin types.

Sun rashes can be easily confused with other sun-related conditions. To determine if you have a sun rash, a healthcare provider will ask you about your sun exposure and may perform a skin biopsy (removing a sample of tissue for examination in the lab).

Other sun-related conditions that are similar to sun rashes include:

  • Solar urticaria: This is a type of hives that is triggered by sunlight. The rash typically appears within minutes of sun exposure and can last for several hours.
  • Photosensitive erythema multiforme: This is a rash that is caused by exposure to sunlight and another trigger, such as a medication or infection. The rash typically appears as red, round patches on the skin.
  • Lupus: This is an autoimmune disease that can cause a variety of symptoms, including skin rashes. The rash associated with lupus is typically red, butterfly-shaped, and appears on the face.

Treatment and home remedies

Treatment for sun rashes depends on the severity and frequency of the condition. Here are some common therapies used for sun rashes:

  • Topical steroids: These can help reduce redness and itching, and shorten healing time. They are usually applied to the rash for 3 to 14 days.
  • Avoiding sun exposure: This is the best way to prevent sun rashes from getting worse. If you must be in the sun, wear protective clothing and sunscreen.
  • Sunscreen: Look for a sunscreen with an SPF of 30 or higher. Apply it liberally to all exposed skin, and reapply every two hours, or more often if you are sweating or swimming.
  • Oral steroids: In severe cases, oral steroids may be prescribed to reduce itching and shorten healing time.
  • Phototherapy: This is a treatment that exposes the skin to gradually increasing amounts of ultraviolet (UV) light. It can help desensitize the skin to sunlight and reduce the risk of future sun rashes.
  • Antimalarial medication: Plaquenil (hydroxychloroquine) is an antimalarial medication that can be an effective treatment for people who do not find relief with sunscreen or phototherapy.

Can you prevent a them?

Sun rashes are not always preventable, but there are ways to reduce your risk. Some basic protective measures include keeping your skin covered, using a broad-spectrum sunscreen with an SPF of 30 or higher, and staying out of the sun during peak hours (10am-4pm). You can also use topical calcipotriene (Dovonex) before exposure to the sun. By following these simple tips, you can help protect your skin from the sun and reduce your risk of developing a rash.

When to see a healthcare provider

Sun rashes can range from mild to severe. They typically cause an incredibly itchy, red rash. In most cases, home treatments, such as steroid cream and sunscreen, can relieve the rash. However, if home remedies do not work, it is important to see a healthcare provider. They can offer additional treatment options and help prevent future sun rashes from developing.


A sun rash is an itchy, red rash that develops after exposure to sunlight. It is caused by an abnormal immune response to ultraviolet (UV) light. They can happen to anyone, but they are more common in females between the ages of 20 and 40 years, and people with a family history of the condition. In most cases, they go away on their own within a few days.

If your rash is severe or does not improve after a few days, you should see a healthcare provider. They can prescribe stronger medications or other treatments. If you have a family history of these rashes, or if you have fair skin, you are more likely to develop them as well. It is important to talk to your doctor about ways to protect your skin from the sun.

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