A double-blind, placebo-controlled study, published in the Achieves of Disease in Childhood (June 2004;89:506-511) evaluated preschool aged children for allergies and ADHD. A group of 277 children was divided into four groups: children without hyperactivity or allergies, children with both conditions, children with ADHD only and children with allergies only. At the start of the study all of the children were placed on an additive-free diet. During the following three weeks, children were randomly given either a placebo or a drink that contained dyes and preservatives. The children were rotated, so that during part of the study the group initially receiving the placebo received the additives, and vice versa.

From the point of view of the parents in this study, the consumption of additives and coloring created hyperactivity. This was true not only for children diagnosed with ADHD or allergies, but also in the population without these diagnoses.