Reply: "Objective Odor Assessment in Patients with Osmidrosis".

Abstract

Dear Sir, We thank Ho et al for their comments1 and encouragement regarding our recently published study,2 and consider the comments very useful for further advancing the field of odors. We have not yet completely identified all the odorants for each individual axillary osmidrosis patient, and we would like to offer our observations below on our failure to detect (E)-e-methyl-2-hexenoic acid (3M2H) and other known odorants that you noted. OUR ODOR SAMPLE COLLECTION METHODOLOGY Odors were collected from T-shirts that were worn for 1 to 2 days immediately before surgery. The sample T-shirts were wrapped in aluminum foil, packed in a Ziploc-type bag, and sent to the laboratory at room temperature. Immediately before gas chromatography-olfactometry/mass spectrometry, a Japanese-government–certified olfactory measurement operator checked the odor to confirm that the target odors were subjectively detected. Because odor analysis is highly dependent on the collection method, the components detected vary widely. Our method is greatly affected by the level of adsorption on the T-shirt, and it is also dependent on the degree to which an odor component is retained on the T-shirt. If it is not adsorbed on the T-shirt in the first place, it will not be detected during analysis, and if it is only weakly retained, the analysis must be conducted immediately after collection. It is thus possible that 3M2H was not detected in our study because of the differences in sampling methods. We might have detected 3M2H had we conducted the analysis immediately after collection or used T-shirts of a different material. However, we can state with confidence that our method of sample collection using T-shirts was not wrong. This is because we were able to confirm the odor by smelling the T-shirts after collection and immediately before testing (and had therefore successfully collected our target odor component). Because the characteristic odor of axillary osmidrosis that was perceived on the collected T-shirts was also confirmed by gas chromatography-olfactometry, we consider that there was no loss during the process between T-shirt collection and analyzer filling. WHAT WE DID TO PROVE THAT 3M2H IS NOT OUR TARGET ODOR We created simulated versions of known causative odors, including 3M2H, although they were not detected in our study. The results for these were different from those of any of the odors that we (the clinicians and the olfactory measurement operator) perceived. Although, of course, axillary odor does not consist of a single odor, it is possible that the target odor may vary between countries and regions depending on genotype, resident microbiota, lifestyle, and diet. Thus, 3M2H may be one of the causative odors of axillary osmidrosis, but although we agree that the odor collection method, storage method, and time to measurement are all crucial, we believe that it is not the main causative odor in Japan. CONCLUSIONS It is possible that 3M2H may not have been detected in this study because of the time taken between T-shirt collection and analysis. However, because the characteristic odor of axillary osmidrosis was perceived on the T-shirts that were collected, and the simulated odor of 3M2H was not our expected target odor, we consider that, in Japan, the odorant is not limited to 3M2H. We will continue studies on more subjects to investigate the possibility that the causative odor may vary from region to region depending on factors such as genetics, diet, and climate. DISCLOSURE The authors have no financial interests in relation to the content of this article.