The red, itchy rash appears to be more an annoyance than a serious health threat, but it has managed to close schools temporarily, worry parents and frustrate school administrators, for whom answers have been elusive.
About 55 students and staff members at Artondale Elementary School in Gig Harbor have been affected by the rash, according to Superintendent Jim Coolican of the Peninsula School District. Artondale has been closed since Tuesday while the district checks the school's ventilation system to see if that might be the cause.
Coolican said last week authorities found an "exceptionally high" level of dust and dandruff in the air.
Students in Pennsylvania, New York, West Virginia, Virginia and Ohio also have complained about rashes on their faces, arms, legs and torsos. For the most part, the rash goes away when a student leaves school.
"For something like this to occur almost simultaneously in different parts of the country is, to my knowledge, unprecedented," said Dr. Norman Sykes, who examined about 30 suburban Philadelphia students who came down with rashes this month.
"People are very concerned about their children," Coolican said. "We say it's not a long-term problem, but people say, 'How do you know? How do you know it won't be a problem for my child 10 years from now?' "
An official at Mary Bridge Children's Health Center in Tacoma said the hospital has seen a few children with rashes. The official also said the rash symptoms subsided once the children left the school.
In addition to checking the ventilation system, staff members at Artondale are removing everything from the school that might add dust to the air. The school is considering working with landscapers to minimize the amount of dust brought in from outside, Coolican said.
Coolican said he had no idea how long the clean-up would last, but his office is making plans for Artondale students to attend other schools when classes resume after winter break Feb. 25.
Although Gig Harbor is checking its ventilation system as a possible cause, most school systems have ruled out environmental factors.
In suburban Philadelphia's Quakertown Community School District, where nearly 170 students at all nine schools were confirmed to have rashes, an environmental company collected air and water samples and examined carpets, floor mats, vacuum bags and clothing, but all tested negative for contaminants.
"We may never know what this thing is," Quakertown Superintendent Jim Scanlon said.
"We sat there itching and then it got all red and bumpy and then it started stinging. I put a paper towel on it so it wouldn't burn that much," said 8-year-old Samantha Makl, who went to the hospital on the first day of the Quakertown outbreak.
Sykes, a dermatologist and professor at Jefferson Medical College in Philadelphia, suspects the culprit in Quakertown is either a mutation of the childhood illness known as fifth disease or a virus not known to science.
Fifth disease, so-called because it once was considered one of the five main childhood illnesses, produces a low fever and cold-like symptoms, followed by a rash that creates a "slapped cheek" appearance and a lacy, red rash on the torso, arms and legs.
Although Sykes' patients had those symptoms, a blood test turned up no evidence of the virus that causes the disease. Sykes then performed a more sophisticated test and found DNA evidence of fifth-disease virus. But nine other students tested negative for fifth disease.
Scanlon, the Quakertown superintendent, thinks some of the rashes might have been caused by psychosomatic "hysteria." And some rashes were not rashes at all — high-school students rubbed themselves with sandpaper in a futile attempt to have the school shut down, he said.
Seattle Times staff reporter Aydrea Walden contributed to this report.