When soaking up the sun brings itchy skin
As the temperature rises, so does our chance to spend time outdoors in short sleeves. But after being out for just a short while on a fine day, have you ever had rashes break out on the parts of your skin that were exposed, and been bothered by itchiness?
When such symptoms show, it may be a disease known as photosensitivity in which the skin is acutely sensitive to light.
How does it happen?
Overexposure to the sun causes sunburn, which occasionally turns to severe, blistering inflammation. This is a common skin reaction even for healthy people, and not indicative of disease.
But for people with photosensitivity, or photosensitive diseases, symptoms are an allergic reaction to sunlight.
The cause for photosensitivity is believed to be skin cells that, upon absorbing sunlight, produce a substance that overstimulates an immune response. However, this substance has yet to be discovered.
Some people who use sunscreen, cold compresses and drugs to lower blood pressure can also experience outbreaks.
This is thought to be because such medicines include chemicals that, when exposed to UV rays, may prompt skin cells to create the substance that cause skin inflammation.
What are symptoms?
Photosensitivity is categorized into different diseases, depending on the symptoms.
• One is called solar urticaria. Hives accompanied by itchiness appear within 10 minutes of being exposed to the sun. These symptoms naturally go away in three to six hours.
• Polymorphic light eruption, or PLE, causes red, spotty and uneven rashes that become itchy. The symptoms appear anywhere from a few hours after exposure to the next day, lingering chronically for several days to more than two weeks.
• Chronic actinic dermatitis has symptoms very similar to those of PLE, but the itchiness is worse. Unable to stop scratching, patients sometimes end up scarring their skin.
• Diseases caused by medicine are photocontact dermatitis, in which rashes appear on areas where a cold compress or sunscreen was applied, and drug-induced photosensitivity, in which rashes appear when patients are exposed to sunlight after taking medicine.
Treatment
When medicine is the cause, the symptoms go away if patients stop taking the medicine. In other cases, in order to relieve itchiness and irritation, patients can take anti-allergy medication or apply steroids to the affected areas.
Professor Akira Kawada, a dermatology expert at Kinki University's Faculty of Medicine, said, “Skin will return to its normal state if patients use medicines for one to two weeks without being exposed to sunlight.”
However, there is no fundamental cure for allergic reactions.
“Symptoms that have cleared up will return if patients are exposed to sunlight again,” Kawada said.
Preventive measures
The most effective preventive measure is to avoid sunlight exposure.
Patients should try not to go out during the daytime, when UV rays are strongest. When they do go out, it is best for them to wear long sleeves and long pants to avoid exposure. Using parasols and hats also helps.
Clothing made of thin, white material can be penetrated by sunlight and therefore provides little protective benefit.
Even those who have never experienced photosensitivity before should be wary as symptoms can suddenly appear in middle age or later.
“I believe there are many people who actually suffer from photosensitive diseases but are wrongly diagnosed as having sunburn or other problems,” Kawada said.
“People need to be especially cautious from April to September when UV rays become stronger. I suggest that people who think they have symptoms similar to those of photosensitive diseases consult with a dermatologist,” he said.