To the Editor:— A recent communication toThe Journalby Keeney on the treatment of hay fever by the oral administration of histaminase may possibly convey the impression that we have been in part responsible for the clinical use of this enzyme. The same impression could be secured from other reports and from the advertising material of the Winthrop Chemical Company. In a review on histamine published by us in 1931 work on histaminase was summarized, and it was pointed out that the presence of the enzyme in various tissues, particularly the kidney, may constitute one of several defense mechanisms possessed by the body for the inactivation of histamine. It was not suggested, nor has this been done in any subsequent publication, that the administration of histaminase might be a useful mode of therapy. Investigations in this laboratory in the period 1930-1932 showed that administration of histamine to animals for