CHICAGO (AP) — New U.S. guidelines for concussions in children recommend against routine X-rays and blood tests for diagnosis.

They also reassure parents that most kids’ symptoms clear up within one to three months.

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The guidelines released Tuesday in JAMA Pediatrics say signs of potentially more serious injuries that may warrant imaging scans include vomiting, unconsciousness and worsening headaches.

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The recommendations are from the U.S. Centers for Disease Control and Prevention. The CDC says it’s the first broad evidence-based advice for diagnosing and treating children’s concussions.

Some 1 million U.S. children get concussions each year although the true frequency is unknown because there is no national effort to track them. The CDC has proposed a surveillance system to fill that gap.

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