We had exactly this problem with my daughter. To cut the story short, it was eventually found that she had an allergy to Tartrazine, an e-additive found in Orange juice. The doctor gave us a medication called Vallergan Forte, which was so strong that when my wife presented it to the chemist, he refused to dipesnse it, saying it must be a mistake as one teaspoon of it would knock a horse out for 24 hours, never minde the 2 teaspoons that were directed. He phoned the doctor and was told to dispense it. It worked. Along with keeping her off the orange juice. My point is, it may be something similar but my daughter might just have been an isolated case.