Summit Medical Group

In this image provided by Summit Medical Group, an unidentified man shows off his case of pityriasis rosea, which often appears in the shape of a Christmas tree.

It may start with a sore throat. After that, there's the aptly-named "herald" patch, a round or oval pink patch that usually shows up on the chest or abdomen, then fades. Days or weeks later, the pink dots start. Sometimes they're on the front, sometimes the back.

And what's really weird is their pattern.

"It was like a tattoo that covered my back in the shape of a Christmas tree," says Mark Jared Zufelt, a 41-year-old Seattle writer/director/photographer, who came down with the rash in his 20s. "It fanned out from the top and worked its way down. It was gross." Zufelt doesn't have a photo of his strange skin condition, but Summit Medical Group has a great example of what the condition, officially called pityriasis rosea, looks like.  

Despite its name, the Christmas tree rash has nothing to do with Christmas trees or even the holiday season. In fact, it usually shows up in the spring and fall, according to Dr. Kenneth Beer, a Palm Beach, Fla., dermatologist.

"Nobody really knows why people get it but a lot of the time, it follows a sore throat or upper respiratory tract infection," he says. Doctors believe the condition is caused by a virus, and it's not thought to be contagious. 

Itchy and scaly (each pink dot is covered with a thin white scale, like cigarette paper), the rash is fairly common and sometimes confused with ringworm, eczema or psoriasis. Beer says he sees about a dozen cases of Christmas tree rash a year, usually in people under the age of 40.

Ironically, his teenage son came down with the worst case he's ever seen.

Dermatlas at Johns Hopkins Medicine

This image provided by Dermatlas at Johns Hopkins Medicine, shows another view of pityriasis rosea.

"He was bright red and had it everywhere -- his chest, abdomen, back, arms, legs," says Beer. "He was miserable."

Treatment for the rash usually involves topical steroids and antibiotics.

"We'll put some people on oral medications but we usually just do topicals," he says. "But the other thing that helps is a little bit of sun or ultraviolet light, UVB. People can go outside and get 15-20 minutes of sun a day or go to their dermatologist's office and use their light boxes." Tanning beds, which primarily give off UVA rays, won't help, he says.

The rash, which Beer terms "uncomfortable but not horrible" usually goes away within two to four weeks with treatment. In addition to topical steroids, oatmeal baths can help alleviate the itching.

While pityriasis rosea has no connection to actual Christmas trees, holiday greenery isn't completely blameless when it comes to allergic reactions.

In 2007, a British teacher named Nicola Coleman made headlines when she broke out in red hives shortly after putting up a Norway spruce. Researchers have also found that some people are allergic to the mold found in pine or fir trees. They've dubbed this allergy -- which triggers a runny nose, sneezing and asthma attacks -- Christmas tree syndrome.

"You can also have contact dermatitis allergies to the sap in some of the trees," says Beer. "But that's totally different."

Zufelt says he doesn't remember what time of year it was when he broke out with his Christmas tree rash, but remembers that it definitely wasn't December.

"I know it wasn't Christmas because that would have been too serendipitous," he says. "It would have made the Christmas card had that been the case."

Related:

Do you hear what I hear? Your brain on Christmas music

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