Sugary, fizzy drinks, all manner of e-numbers (especially the yellow/orange colourings they use, such as on fish fingers). By process of elimination, you can find out what your child tolerates and what it doesn't. However, one of my children was very hyper active, and tests concluded that it wasn't from any food intolerance or allergies, but rather from a faulty gene. I was told that after a certain age, the symptoms should start to wear off, with no long-lasting ill effects. This's now happened - thankfully. I was offered Ritalin, which I refused, as research into it at the time led me to believe that it can alter a child's personality permanently. Our doctor said he agreed with me, and all's now well, so the best of luck to you.