Withdrawal of Claim that Azo Blue Causes Congenital Malformations

Abstract

In a recent paper by the author in Proc. Soc.Exptl. Biol. and Med. 85: 319-322. 1954, data were presented indicating that injection of a solution of azo blue into pregnant rats caused congenital malformations in the offspring. The dye was subsequently analyzed and found to be not azo blue but the closely related dye trypan blue. It thus becomes necessary to withdraw the claim that azo blue causes malformations as described. Results attributed to azo blue become valid if ascribed, instead, to trypan blue. All other observations stand as presented in the original paper.