A national study of recent rash outbreaks in school children has found no common cause, the Centers for Disease Control and Prevention said Thursday.

Fourteen states have reported some type of rash outbreak since October, most often among elementary school children who complained of mysterious rashes on their faces, arms, legs and bodies. The outbreaks have affected anywhere from 10 to 600 people at a time.

In Pennsylvania, an outbreak of red, itchy rashes at five schools worried parents and temporarily closed some schools. A Connecticut school also closed for one day to clean air filters after children developed rashes.

The CDC requested reports from all 50 states about any rash outbreaks but found no common cause for the rashes and said the rashes weren't all the same.

"With 53 million young people attending 117,000 schools every day in the United States, it is expected that rashes from a wide variety of causes will be observed," the study concluded.

Researchers said further study is needed because many of the outbreaks have unexplained causes, even after interviewing doctors who treated the rashes and doing environmental studies of the schools that had outbreaks.

Rash outbreaks were reported in Arizona, Connecticut, Florida, Georgia, Indiana, Mississippi, New York, Ohio, Oregon, Pennsylvania, Texas, Virginia, Washington and West Virginia.

Most of the rashes went away in less than two weeks.