Allura Red AC is a food dye that is also known as E129, FD&C Red 40, Allura Red, Food Red 17, C.I. 16035, 2-napththalenesulfonic acid, and by two other chemical names you will never see on a food product label, disodium 6-hydroxy-5-((2-methoxy-5-methyl-4sulfophenyl)azo)-2-naphthalenesulfonate and 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo-)disodium salt. Allura Red AC was first introduced into food manufacturing in the United States as a substitute for the red dye that had been made from coal tar that was called amaranth, named after the color, not after the plant.
Ironically, one of the reasons Allura AC caught on was that there were predictable problems with the natural food coloring agent made from amaranth (E123 in the EU system). The plant dye caused a skin and throat reaction similar to touching or drinking stinging nettles in some people. It turns out that Allura Red AC produces similar problems, but it's actually less irritating than the plant dye it replaces.
Where do you find Allura Red AC? In the USA there is a soft drink that's mostly sugar, carbonation, and Allura Red AC known as Big Red. Even people possessed of a sweet tooth often find it a bit sugary. To keep the drink from looking like the bubbly sugar water it is, manufacturers add this bright red dye. Allura Red AC is also added to strawberry juice and cranberry juice to make them more alluringly red.
What kinds of problems can Allura Red AC cause? In addition to reports of symptoms similar to aspirin allergy, studies in the UK and Ireland suggest that high levels of consumptions of dyes chemically similar to Allura Red AC may aggravate the symptoms of ADHD in children and teens. There have been studies of possible links of Allura Red AC to colon cancer in lab rats, but the amounts of Allura Red AC given the laboratory animals (1 mg per kilogram of body weight) were analogous to drinking soft drinks that were half red dye and half water—or drinking several hundred sodas or juice boxes every day. You should not worry that you might have given yourself cancer if you have consumed products containing this dye in the past.
But should you be consuming Allura Red AC now? It can cause some of the same kinds of problems as tartrazine. About 1 in 300 users may come down with hives or a rash similar to a stinging nettle allergy. About 1 in 1000 users may come down with an autoimmune reaction causing migraines, dizziness, anxiety, agitation, constipation, nausea, or blurred vision similar to the reactions caused by tartrazine, but usually not as severe as the reactions caused by tartrazine.
Several countries in the European Union banned Allura Red AC and were forced by the European Union to reinstate its use. The Center for Science in the Public Interest has called for a ban in the USA, but the US Food and Drug Administration has not yet responded.
Small amounts of Allura Red AC are not likely to hurt you—but why take a chance. It's always best to choose organic juices or, even better, make your own fruit and vegetables juices at home.