Mechanism of Poisoning From Wax Crayons

Severe poisoning from ingestion of wax crayons was reported by Brieger and others and discussed in an editorial inThe Journal. Since then, additional cases have come to our attention. Methemoglobinemia was the chief sign of intoxication in all human cases; it was reproduced in one-third of a group of cats fed red and red-orange crayons. The pigment used in certain brands of such crayons was para red, a dye considered insoluble and harmless. Oral or intravenous administration of para red to rats, dogs, and cats has not resulted in methemoglobinemia. However, the intermediate of this dye, p-nitroaniline, is a methemoglobin-forming substance. Since only a small percentage of children who are known to have ingested pieces of crayons have become affected, the following explanations of this type of poisoning were given consideration: (a) presence of unreacted amines in some batches of the dye; (b) catabolization of the dye to methemoglobin-forming