Ponceau 4R (Molecule of the Month for September 2007)
E124, Food Red 7, C.I. 16255, Cochineal Red A, New Coccine, Acid Red 18, SX purple
Ponceau 4R is a synthetic colourant that may be added to foods. It is denoted by E Number E124. Ponceau 4R is a red azo dye which can be used in a variety of food products.
Ponceau 4R is considered carcinogenic in some countries, including the USA, Norway, and Finland, and it is currently listed as a banned substance by the U.S. Food and Drug Administration (FDA).  Since 2000, the FDA has seized Chinese-produced haw flakes (a fruit candy) on numerous occasions for containing Ponceau 4R.
A study commissioned by the UK's Food Standards Agency found that when used in a mixture of other colourants and preservatives, increased levels of hyperactivity in children were observed.
Update by Karl Harrrison
(Molecule of the Month for September 2007 )