Foods with certain artificial colourants can cause allergic reactions in some people, according to the Federation of German Consumer Organisations.
However, products that are coloured with fruit or plant extracts are safe. This, for instance, is standard practice with organic produce in the European Union, where the use of artificial colourants is not permitted.
Allergic reactions to artificial colourants include hives, asthma and dermal oedema. The problematic substances and other additives appear as so-called E numbers on the product label.
According to consumer watchdogs, these include the colourant Quinoline Yellow (E104) and the azoic dyes Tartrazine (E102), Sunset Yellow (E110), Azorubine (E122), Cochineal Red (E124a) and Allura Red (E129).