Frankfurt, Germany - Children's sweets are often made with what are known as azo dyes to make them appear very colourful.

This group of dyes includes additives such as tartrazine, carmoisine and quinoline yellow which may cause damage to health, according the Frankfurt-based Consumer Protection Office in the German state of Hesse.

These dyes not only cause allergic reactions, but they are also believed to cause intensify hyperactivity in children and making it difficult for them to concentrate.

The same doubts apply to another food additive, benzoic acid. There are also suspicions that the colouring quinoline yellow could be carcinogenic.

A study conducted by the state's Consumer Protection Office found that almost half or 44 per cent of the supermarkets visited in Frankfurt had food products with azo dyes.

Three per cent of the food products aimed at children, and drink products in particular, also contained benzoates as preservatives.

According to EU regulations, such products will have to have a warning notice on their packaging by 2010. The states' Consumer Protection Office has called for a complete ban on these additives. (dpa)