Solar Urticaria Overview

an itching skin condition all over the legs. Front and back view.
Solar urticaria is a rare skin condition caused by an allergic reaction to the sun. See more pictures of skin problems.
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Grab your sunglasses, bathing suit and sunscreen. A sunny day is an invitation to have fun and relax outdoors. For some people, though, exposure to sunlight causes urticaria (pronounced ur-tuh-KAR-ee-uh) -- another word for hives.

Hives is a common allergic reaction that causes itchy, red welts on the skin. About 20 percent of the population will experience urticaria at least once [source: Asthma and Allergy Foundation of America]. Some of the most common causes are allergic reactions to certain medications and foods (shellfish and nuts, for example), pet dander, pollen and even stress. Solar urticaria is a rare form of hives caused by an allergic reaction to sunlight.


If you get an itchy rash on your skin when you are out in the sun, there's a good chance it's probably something other than solar urticaria. This form of hives affects only about three in 100,000 people worldwide [source: Clinuvel Pharmaceuticals Ltd.]. Anyone can get solar urticaria, but those who are most likely to experience it are women and people younger than age 40 [source: Salford Royal].

Solar urticaria is a true allergy to sunlight. It happens when skin is exposed, even for a few minutes, to ultraviolet (UV) radiation -- rays that can't be seen and can cause damage to the eyes and skin. Sunlight, commercial tanning beds and tanning lamps all produce ultraviolet rays. When the skin of a person with solar urticaria is exposed to UV radiation, it erupts with a nasty, red rash. This happens most often in spring and summer on skin that was normally covered in the winter, such as the arms, upper chest and lower legs.

The condition's cause is still unknown, but some experts believe it might be related to a reaction from the body's immune system [source: Baron, Asthma and Allergy Foundation of America.]

The more you know about this unpleasant reaction to sunlight, the better prepared you will be to enjoy the outdoors with your family and friends. But how do you know whether you have solar urticaria? Find out by learning the symptoms on the next page.


Solar Urticaria Symptoms

If you develop a rash after exposure to sunlight, you might be experiencing solar urticaria. The rash can vary from person to person and might include

  • Small, raised bumps
  • Redness
  • An itching or burning sensation
  • Swelling or blistering on exposed areas

These symptoms often show up on skin that was newly exposed to the sunlight. Skin that is always exposed, such as the face and hands, might not break out. Also, even though some skin might have been covered by clothing, it can still show these symptoms, too [New Zealand Dermatological Society].


Solar urticaria usually appears within half an hour of exposure to sunlight and typically goes away quickly. If the skin is protected from the sun, the rash should disappear within a few hours and almost always within a day [source: Baron]. If the rash is exposed to more sunlight, it could be dangerous [source: Salford Royal]. In some people, solar urticaria reoccurs and becomes a chronic condition [source: Asthma and Allergy Foundation of America].

People with solar urticaria also might feel sick. Other symptoms can include headache, nausea or fainting [source: Baron]. You should consult your doctor if the rash persists or worsens, or if it covers a large area of your body that was protected by clothing. You should seek medical attention immediately if the rash is accompanied by swelling around your lips or eyes, or if you have trouble breathing or swallowing, or feel faint. These can be serious signs of an allergic reaction and might be symptoms of something other than solar urticaria [source: Harvard Medical School].

Now that you know what to look for, read on to learn how to treat it.


Solar Urticaria Treatments

Solar urticaria can be uncomfortable, but there are treatments you can perform at home to reduce the redness and itching. Cool water will help to soothe your irritated skin. Applying cold compresses takes the heat out of the rash, as does a cool soak in the bathtub. Over-the-counter medications, such as antihistamines, can provide even more relief. Ibuprofen, used as directed, can ease the soreness, and anti-itch or hydrocortisone cream can significantly reduce the itching. Before using any over-the-counter medications, be sure to ask your doctor or pharmacist about possible interactions with any prescription medications that you take. Overall, the best thing you can do to treat solar urticaria is to stay out of the sun.

A severe case of solar urticaria requires treatment by a doctor. When home remedies and over-the-counter treatments don't work, your doctor might prescribe a prescription-strength antihistamine and a steroid-based cream [source: Harvard Medical School]. In extreme cases, the doctor will require additional tests and prescribe a treatment that is right for you. Often, this treatment involves phototherapy -- controlled exposure of your skin to sunlight to desensitize your body's allergic reaction to the sun [source: Salford Royal].


Solar urticaria is a rare form of sun allergy. Chances are that hives you get from sunlight are not true solar urticaria. More often, a sun rash is caused by a chemical reaction from a substance on your skin, such as perfume or lotion. Certain medications can also increase your sensitivity to sunlight and cause hives.

Solar urticaria can be difficult to diagnose. If you get a persistent rash from exposure to sunlight, especially if it is severe and accompanied by flu-like symptoms, you should see your doctor. To learn more about solar urticaria, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles

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  • American Academy of Dermatology. "Sunscreens/Sunblocks." 2005. (Accessed 8/2/09)
  • American College of Allergy, Asthma & Immunology. "Urticaria." March 2005. (Accessed 8/2/09)
  • Asthma and Allergy Foundation of America (AAFA). "Chronic Urticaria (Hives)." 2005. (Accessed 8/2/09)
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