Colours and preservatives are only two of the many classes of additives in food but they are of interest because many reported cases of sensitivity involve these two groups of substances. Preservatives present the greatest potential health hazard being, by definition, biologically active. Colours and other additives are required to perform a technological function whilst remaining as biologically inert as possible. Food additives are controlled by the Food and Drugs Act 1955 on the basis of advice from the Food Advisory Committee (FAC). Lists of the permitted preservatives and colourings are available, together with details of restrictions on their uses; this information is continually being updated. Food labelling regulations mean that some information about additives can be determined from the labelling--but even if an additive is not listed on the package, one cannot always assume that it is not present in the product, since additives coming through in the original ingredients need not always be listed. Other exemptions also exist, so there can be no absolute certainty about the presence, or absence, of a specific additive. That information can only be obtained by contacting the manufacturer.