60 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS decomposed by alkali and strong acids to give a variety of products. The pH value of a saturated solution is 5-5, and it is recommended that the solution should be kept at a slightly acid pH value. The constitution of allantoin has been shown to be H N -- .CO øc/ N -- CH -- NH.CO.NH• N * Examination of the above formula shows that it contains an asymmetric carbon atom (*). The allantoin should therefore exist in two optically active forms, but early attempts to isolate these forms were, however, unsuccessful. 2o However, dl allantoin was resolved by Fosse, Thomas and de Graeve, 2• who isolated the 'T' form by treating the allantoin with an enzyme from soya which preferentially fermented the "d" form. The "d" form is probably the one that occurs naturally, and has now been isolated from calves' urine and certain plants by extraction methods avoiding all temperature rises. The "d" and 'T' forms are both readily racemised even by warming in aqueous solution. Theease of racemisation is now known to be the reason for the failure of the early attempts at separation. The ready racemisation is almost certainly due to a keto-enol tautomerism existing between the asym- metric carbon atom and the neighbouring keto group. In view of this tautomerism, in order to maintain optical activity, solutions should be kept at pH values slightly less than 7. Allantoin is amphoteric forming salts with both acids and bases. Ammonium, TM piperazine 2• and bismuth 2' allantoinates have been used therapeutically, but they offer no advantage over the allantoin itself. CONCLUSIONS By analogy with other optically active systems, there should be a biological difference between "d" an 'T' allantoin on the one hand as well as between them and racemic allantoin on the other. It is apparently the "d" form which normally functions in the living plant and animal. When racemic allantoin is applied therapeutically, it may be presumed that only one-half of it is active, while the other half may be inert or could even be in part an inhibitor or poison. No practical work has, however, been done on this aspect of allantoin therapy. However, it is almost certain that the allantoin in the extract of comfrey would be racemic, since the extract was obtained with the aid of heat. The latest use of allantoin has been in association with the sulphanilamide drugs, where it has been used in cases of impetigo, dermaphytosis, pyoderma,

ALLANTOIN--ITS PROPERTIES AND USES 61 folliculitis." ,Twq cases of seborrhoeic der,matiti, s h,ave, ,been treated with this sys. tem."' The secondary symptoms of the.latter, due to infection, were cleired within 'three' weeks. O/:her uses for this coi•binatiSn' have been in the preparation of wounds' for skin grafting and in controlling wound infections. In this combination can be seen a similarity to maggot therapy in that the sulphanilamide provides the bactericidal properties m)rmally provided by the maggots, which are absent when allant0in alone is used. It can be seen from the above account that the work reported on allantoin therapy is somewhat unlikely to be of great use in the cosmetic industry unless its alleged properties are more firmly established than hereto. It is of interest to note that allantoin is omitted fro m the latest editions of the Pharmacopoeia. The author wishes to thank the directors of County Laboratories Ltd. for their permission to publish this paper. REFERENCES Macalis. ter, B.3//.J., 1912, i, 10. Macalister, Th• Symphytum OJficinale and Its Contained A lla,ntoin, John Bale, Sons & Danielsson Ltd., London, 1936. Baer, J. Bon• & Joint Surgery, 13, 438 (1931). Robinson, J. Bon• • Joint Surgery, 17, 267 (1935). Robinson and Norwood, J. Lab. • Clin. 31ed., 19, 581 (1933-34). Robinson and Norwood, J. Bone & Joint Surgery, 15, 409 (1933). Livingston, J. Bon• & Joint Surgery, 18, 751, (1936). Livingston, Am. J. of Surgery, 35, 554 (1937). Greenbaum, 1938, U.S. pat. 2,124,295 .... Bethune, J. Thoracic Surgery, 5, 322 (1936). Gordon, Intern. J. Orthodontia, 23, 840 (1937). Kaplan, J.A.31. A., 168 (1937). Greenbaum, J. Am. Pharm. Assn., Sci. Ed., 31,263 (1942). Sussman, Dental Items of Interest, 59, 510 (1937). Shipp and Hetherington, Proc. Soc. Exp. Biol. and 31ed., 35, 180 (1936-37). Pomerat, Proc. Soc. oexp. Biol. and 31ed. , 51,345 (1942). See (2). ' Berthelot and Bertrand [see (2)]. See (2). Mendel and Dakin, J. Biol. Chem., ?, 153 (1909). Fosse, Thomas and deGraeve, C.R., 198, 689 (1934). Robinson and Spring, 1942, U.S. Pat. 2,303,765. Greenbaum, J. Am. Pharm. Assn., Sci. Ed., •1,263 (1942). Engels, Rahway and Stein, U.S. Pat. 2,104,738. Niedelman and Horoschok, Urolog. •, Cutan. Rev., 48, 172 (1944).