The little girl's brother George struggled to answer questions on whether or not he missed drinking milk, obviously distracted by his sister's antics.
The girl's mother managed to keep a straight face, giving her views on raising children with the allergy.
Having stifled laughter throughout the broadcast, the veteran newscaster joked: "Mary Nightingale, I think, will have a more peaceful time at 6.30pm".
Viewers and journalists took to Twitter to share their amusement about the ITV Lunchtime News incident.
The hilarious incident is reminiscent of the interview with South Korean expert Robert Kelly, which was gatecrashed by his two young children.
As Kelly discussed questions on the country's president being ousted from power, a toddler burst into the room and performed a comical dance behind him.
Kelly, an associate professor at Pusan National University in Busan, and his offspring became an overnight sensation after the interview aired on BBC News.
