It was Trenton Shutters’ first week at preschool when the typically easy-going 4-year-old took an alarming turn for the worst.

“He started melting down several times a week and was unable to recover,” recalls Trenton’s mom, Renee Shutters. “One day he’d be fine, the next he would get angry and not like himself. We thought he was bipolar. I was scared.”

After months of trying to pinpoint a trigger, Trenton’s mother and teacher drew an intriguing conclusion: On days Trenton had orange cheese puffs, blue sugar-free yogurt, or the other colorful fare often provided for snack at school, his attention cratered. And on the nights when his mom gave in and let him have a neon gumball at hockey practice, a temper tantrum was sure to ensue. Skeptically, Renee took the advice of a friend, purged her cupboard of anything containing artificial food color, and asked his teachers to keep him away from dyes as well.

 “We saw an improvement within days,” says Shutters, who lives in Jamestown, New York. “Trenton is a model student now.”

Shutters is among dozens of parents, physicians and researchers who will converge on Washington, DC March 30 and 31 to urge a U.S. Food and Drug Administration (FDA) panel to recommend a ban of—or at least warning labels on—foods containing synthetic dyes.

Their allegation—that the petroleum-based colorants can lead to behavior problems, allergies and possibly cancer—dates back to the 1960s, when San Francisco allergist Ben Feingold reported that his patients’ radically improved when they kicked dyes. With few legitimate studies verifying the link, Feingold’s theories were largely dismissed. But thanks to a series of highly respected European trials connecting dyes to attention disorders, the European Parliament moved in 2010 to require warning labels on foods that contain them. Now U.S. regulators are taking a fresh look at artificial colors and their potential health hazards as well.

“Just the fact that FDA is holding this hearing is very significant,” says Michael Jacobson, executive director of the Center for Science in the Public Interest (CSPI), which called for the meeting. “It sends a message that this is a topic worthy of discussion.”