Sun Rash

Rash on the leg of a one year old girl.
Getting Beautiful Skin Image Gallery Sun rash is caused by an allergic reaction to sunlight. See more pictures of getting beautiful skin.
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It's common knowledge too much sun isn't good for you. In addition to causing painful sunburns, it also puts you at higher risk for skin cancer. Yet, for others, sun exposure can cause another painful condition: sun rash.

Sun rash is an allergic reaction to sunlight. A few different allergies can cause sun rash, the most common being polymorphous light eruption (PMLE), a condition in which skin rashes can develop after fairly limited sun exposure. Other sun allergies that cause sun rash include hereditary PMLE, which is often found in people of Native American descent, and solar urticaria, a rare condition characterized by hives that usually affects young women.


Certain medications can also cause allergic reactions to the sun known as photoallergic reactions. These reactions are caused by the interaction between sunlight and certain ingredients in the medications. Common prescription medications that can cause photoallergic reactions include birth control, antibiotics and antidepressants.

The physical effects of PMLE vary, but they usually take the form of small bumps, redness and itchiness, and sometimes burning, blistering or swelling can occur as well. This rash typically appears on the neck and chest, but it can also show up on the arms and thighs. Other symptoms include chills, headaches and nausea.

PMLE occurs in an estimated 10 to 15 percent of the population and affects people of all races and ethnicities [source: Intelihealth]. People with PMLE typically exhibit symptoms at the same time each year, which is usually in the spring or early summer when sun exposure first occurs.

Read on to learn more about sun rash and how to treat it.


Sun Rash Causes

People who get sun rash are photosensitive, which means they're sensitive to sunlight. Why certain people are more sensitive to sunlight is unknown, but what triggers the rash is ultraviolet light [source: Mayo Clinic].

The sun's rays are composed of three different types of ultraviolet, or UV, radiation: UVA rays, UVB rays and UVC rays. UVC rays aren't a factor in sun rash because they never reach the Earth. UVA rays most commonly cause PMLE; however, some people react to UVB rays or to a combination of UVA and UVB rays. People with PMLE can also have allergic reactions to tanning beds because they emit UV radiation.


If you have PMLE and live in a northern climate, your first exposure to sunlight in spring or early summer is more likely to cause sun rash because your skin hasn't seen the sun for months. Taking a sunny vacation during the winter can also trigger PMLE for the same reason. Fortunately, each time the skin is exposed to the sun, sensitivity to UV light usually decreases. By the end of the summer, people with PMLE often are able to enjoy the sun's rays without getting a rash.

Anyone can be affected by PMLE; however, some common risk factors include being female, being under 30, being fair-skinned, living in a northern climate and having a family history of PMLE [source: Mayo Clinic].

Now that you know what causes sun rash, read on to learn how to treat and prevent it.


Treating Sun Rash

Sun rash usually shows up one to two hours after sun exposure. The rash can disappear within two to three days, but it may last more than a week. Fortunately, these rashes rarely leave scars.

Common home remedies for treating sun rash include applying a cold compress to the affected areas, using hydrocortisone cream, taking antihistamines to lessen the allergic reaction or taking anti-inflammatory drugs, such as aspirin or ibuprofen, to reduce redness and swelling. If blisters appear, cover them with gauze and avoid popping them [source: Mayo Clinic].


You should see a doctor if your sun rash covers more areas of your body than just the neck, chest, arms or thighs, or if it begins to blister painfully or you start to run a high fever. Also talk to your doctor if you're on any medications that might have caused a photoallergic reaction. Your doctor may prescribe a strong antihistamine or recommend a technique called hardening, which involves gradually increasing your skin's exposure to sunlight [source: American Osteopathic College of Dermatology]. If your doctor offers hardening through phototherapy, he or she will expose you to doses of artificial UV light for a prescribed amount of time.

Preventing Sun Rash

If you're sensitive to sunlight, the best way to prevent sun rash is to simply stay out of the sun. However, if you have to be outdoors, consider these other ways to protect yourself from PMLE and other sun allergies. First, try to limit your sun exposure as much as possible. If you've experienced PMLE in the past, talk to your doctor about phototherapy and hardening. You can also try slowly increasing your sun exposure in the spring and early summer. Avoid being in the sun between the hours of 10 a.m. and 4 p.m. when the sun is most intense [source: American Osteopathic College of Dermatology].

If you have to be in the sun during its peak hours, protect yourself by wearing light clothing that covers most of your skin. You should also wear sunscreen with a sun protection factor of at least 15 and reapply it every two hours and after swimming or sweating heavily. Try to find a sunscreen that protects your skin from both UVA and UVB rays, and remember to wear sunscreen even on cloudy days. UV rays can harm more than just your skin, so wear sunglasses and use lip protection that contains sunscreen.


Regardless of whether you're affected by a sun allergy, following these prevention tips can protect your skin from UV rays while still allowing you to soak up some sun.

For more information on sun rash, check out the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Aetna Intelihealth. "Sun Allergy (Photosensitivity)." (Accessed 7/25/09)
  • American Academy of Dermatology. "The Sun and Your Skin." (Accessed 7/25/09)
  • American Osteopathic College of Dermatology. "Polymorphous Light Eruption." (Accessed 7/25/09)
  • Centers for Disease Control and Prevention. "Skin Cancer: Prevention." (Accessed 7/29/09)
  • "Heat Rash." (Accessed 7/27/09)
  • "Polymorphous Light Eruption." (Accessed 7/25/09)
  • Scheinfeld, Noah S. "Polymorphous Light Eruption." Emedicine from WebMD. March 13, 2008. (Accessed 7/29/09)
  • Zhang, Alexandra Y. "Drug-induced Photosensitivity." Emedicine from WebMD. March 19, 2007. (Accessed 7/29/09)