Sun Allergies: When the Sun Is the Enemy

Thursday , August 23, 2007

By Christine Buske



Although most people dread the end of summer, about 20 percent of the population is anticipating the overcast days of fall.

For most of us, summer brings cold treats, days at the beach and a chance to go out and enjoy it all. To others, the summer feels more like house arrest. These are people affected by sun hypersensitivities, more commonly referred to as sun allergy.

Polymorphic Light Eruption

This type of allergic reaction is characterized by the formation of bumpy and itchy rashes on sun-exposed skin. But it is not actually an allergy to the sun. Rather, it is an immune reaction called polymorphic light eruption (PMLE).

“Most sun sensitivities occur in areas where there are four seasons,” said Dr. Debra Wattenberg, associate professor of dermatology at Mount Sinai Hospital in New York.

Considering the immune system reacts to the “unknown,” it is easy to understand why, in some individuals, this protective mechanism goes into overdrive. After all, for the entire winter, most skin — at least that of individuals living in colder climates — is not exposed to the sun. This is why countries in the northern hemisphere have the largest percentage of affected individuals.

Having skin that is hypersensitive to the sun is different from having a fair complexion that is susceptible to sunburn.

PMLE is looks like, and is often confused with, hives. The rash-like appearance makes it easy to spot and tell apart from sunburn.

“Often the patient complains of a transient, itchy, and bumpy eruption in the early to mid spring,” said Dr. Laurie Polis, who teaches at the Mount Sinai department of dermatology. “In the north, there is a greater contrast in the seasonal exposure to the sun.”

PMLE is essentially an immune reaction to UV rays, and “with chronic exposure, most individuals will stop reacting to the immune reactions caused by the sun,” said Wattenberg.

Persons should be aware, however, that stubbornly basking in the sun before letting the rash clear up only causes it to become more severe and painful.

Ideally, anyone already aware they have the condition should slowly build up their tolerance to sunlight starting in the early summer months. A reaction is more likely to develop during rapid long-term exposure to the sun following a winter of sun deprivation.

Patients with severe PMLE can even develop it throughout the winter as well. But, for most, the rashes will clear up as the summer progresses and the skin becomes accommodated to the ultraviolet (UV) rays.

Lather on Sunscreen

Using proper sun protection is important for everyone to decrease the risk of skin cancer, however, it is even more important for those who have chronic PMLE.

“Use a broad spectrum sun screen that blocks UVA rays and contains zinc or titanium dioxide,” said Wattenberg, as well as using “hats, and photo-protective clothing.”

Additionally, “individuals (with PMLE) should learn to limit their sun exposure between the hours of 10 a.m. to 2 p.m.,” said Wattenberg.

In more severe cases, treatment with antihistamines or topical cortisone can provide relief and allow patients to lead a normal life.

Although sun sensitivities can produce severe skin reactions, they are “luckily not associated with an increased risk of skin cancer,” said Wattenberg.