Britney Spears’s trip home with her sons this weekend took a serious unexpected turn when her 2-year-old son Jayden was rushed to a Kentwood-area hospital at 1:30 p.m. Sunday. But the toddler is “fine,” according to a source close to the family.

Jayden was taken to the hospital after suffering “a terrible allergic reaction. He had hives, was itchy and irritable,” according to the source, who says that Britney Spears and her mother, Lynne, spent the night at the hospital with Jayden.

As for what caused the reaction, “They’re just not sure,” said the source. Just prior to the incident, Britney, Jamie Lynn, Bryan, Lynne and Jamie Spears were enjoying a fun afternoon at the family’s Serenity mansion, the boys’ first trip out of California with their mother since she lost custody.

A rep for the family had no comment, and rep for Britney’s ex-husband Kevin Federline also had no comment.