What Does a Sun Rash Look Like?

A sun rash—medically known as polymorphic light eruption—is a red, itchy rash that appears on the skin due to sunlight exposure. Sometimes confused with a sun allergy, a sun rash is an autoimmune response that begins in the spring and typically ends by fall.

This article will cover what a sun rash looks like, its symptoms, causes, and treatment. It will also discuss preventive measures to avoid developing the condition.

Sun Rash Image

Sun rashes appear after sun exposure to the skin. It only takes 30 minutes of sun exposure to trigger the rash. It can develop within a few minutes to hours after exposure. The rash typically resolves within 14 days without leaving a scar.

Sun rashes can present in several ways. The most common form is the papular sun rash. This looks like small, red, smooth-topped bumps situated close together, all in the same area.

These bumps can then form raised red patches called plaques. These typically appear on the arms, legs, and chest. Plaques can also include fluid-filled blistered areas called vesicles.

Symptoms of a Sun Rash

Sun rashes can present after exposure to the sun. The rash will heal if the skin is covered and not exposed to additional sunlight.

It is most often experienced in females age 20 through 40.

The symptoms of a sun rash vary and can include:

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

For most people, gradual sun exposure leads to what is known as hardening. This is when the skin becomes less sensitive to light with repeated sun exposure. People who are exposed to sunlight all year rarely develop sun rashes.

The sun rashes tend to begin in small areas but these patches expand during succeeding summers. Many people will have sun rash flares each summer. Each person will have a different tolerance to how much sunlight they can be exposed to before they develop a sun rash.

What Causes a Sun Rash?

A sun rash is caused when a combination of certain factors all come together.

Autoimmune Condition

Researchers believe an autoimmune response to sunlight causes sun rashes.

Medically, sun rash is described as a type 4 delayed hypersensitivity immunological reaction. During this reaction, the T cell does not function properly, which causes a decrease in the normal immune suppression in the skin caused by ultraviolet (UV) light. This then creates an inflammatory response.

UV Radiation

When a sun rash occurs, there is a delayed, abnormal response to UV light exposure from antigens in the skin. This causes an inflammatory response. Sun rashes are caused by ultraviolet A (UVA) radiation in 75% to 90% of cases and can even occur when sunlight comes through a window. Ultraviolet B (UVB), the primary cause of sunburns, can also cause sun rashes.

Genetics

People prone to sun rashes usually have a genetic component to the condition that causes it to occur when combined with environmental factors. A family history of sun rashes is found in 10% to 63% of sun rash cases.

Risk Factors for Sun Rashes

Having certain risk factors can increase the likelihood of developing a condition. If someone has a risk factor, it does not mean they will have the condition. Below are the risk factors for sun rashes:

• Female gender
• Ages 20 to 40 years old
• Family history of sun rash
• Living in a temperate climate
• People with Fitzpatrick skin type 1
  

Sun Rash vs. Other Sun-Related Conditions

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

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

• Solar urticaria
• Photosensitive erythema multiforme
• Lupus

Treatment and Home Remedies

Treating a sun rash will depend on the severity and frequency of the condition. The following treatments are common therapies used for sun rashes:

• Topical steroids: A three- to 14-day course of topical steroids can reduce the redness and itching to shorten healing time.
• Avoid sun exposure: Staying out of the sun, especially between 11 a.m. and 3 p.m. will protect the skin and reduce the likelihood of worsening the rash.
• Sunscreens: Look for sunscreens with maximum protection to shield skin from the sun's harmful UV rays.
• Oral steroids: In severe cases of sun rash, oral steroids are taken to reduce itching and shorten healing time.
• Phototherapy: Phototherapy is a common treatment used as a way to desensitize the skin with repeated sunlight exposures to cause hardening.
• Antimalarial medication: Plaquenil (hydroxychloroquine) is an antimalarial medication that can be an effective treatment for people who do not find relief with sunscreen and do not respond to phototherapy.

Can You Prevent a Sun Rash?

While not every sun rash can be prevented, there are ways to keep your skin safe and decrease the chances of developing the condition.

Basic protective measures like keeping skin covered, using a broad-spectrum sunscreen, and staying out of the sun are all ways to prevent a sun rash.

Another option is using topical calcipotriene (Dovonex) before exposure to the sun.

When to See a Healthcare Provider

A sun rash can be a mild to serious condition that causes an incredibly itchy, red rash. When home treatments like steroid cream and sunscreen do not relieve the rash, it is time to contact a healthcare provider. They can give additional treatment options and provide ways to prevent future sun rashes from developing.

Summary

A sun rash is an itchy, red rash that develops after exposure to sunlight. It can happen to anyone but is most common in females between the ages of 20 and 40 years, and people with a family history of the condition. Treatment is aimed at reducing symptoms and preventing future rashes. Talk to a healthcare provider if home treatment does not work or symptoms worsen.