Yellow food colouring produced synthetically from petroleum. Many people are allergic to foods containing it. Typical effects are skin disorders and respiratory problems. It has been shown to have an adverse effect on hyperactive children.
Red and white are the colours of Bohemia, dating back to the 13th century. Blue represents Moravia. Unlike that of the Slovak Republic, the Czech flag is not based on the pan-Slav colours. Effective date: 1 January 1993.