Or simply misunderstood? That's what some doctors are finding, according to the New York Times, and that's potentially dangerous because parents then limit their children's diets, sometimes to extreme. Says the article:
Doctors say that misdiagnosed food allergies appear to be on the rise, and countless families are needlessly avoiding certain foods and spending hundreds of dollars on costly nonallergenic supplements. In extreme cases, misdiagnosed allergies have put children at risk for malnutrition.