We believe readers should be able to check the research for themselves. Below are the primary scientific sources referenced in this article.
1. Haze S, Gozu Y, Nakamura S, et al. (2001).
2-Nonenal Newly Found in Human Body Odor Tends to Increase With Aging.
Journal of Investigative Dermatology, 116(4), 520–524.
This is the study that identified 2-nonenal in the 40+ participants studied and linked it with age-related changes in skin lipids.
2. Mitro S, Gordon AR, Olsson MJ, Lundström JN. (2012).
The Smell of Age: Perception and Discrimination of Body Odors of Different Ages.
PLOS ONE, 7(5), e38110.
This controlled study tested whether people could distinguish age groups using body odor alone.
3. Dalton P, Wysocki CJ. (1996).
The Nature and Duration of Adaptation Following Long-Term Odor Exposure.
Perception & Psychophysics, 58(5), 781–792.
Participants exposed to the same odor in their homes for two weeks became less sensitive to that specific odor — the phenomenon commonly described as “nose blindness.”
4. Tatsuguchi I, Matsuoka T, Izumi R, Ijichi S, Shibata H. (2012).
Preventive Effect Against the Aged Men’s Body Odor by the Soap Containing Polyphenol.
Journal of Japan Association on Odor Environment, 43(5), 362–366.
A four-week study of 20 men aged 43–75 found significant reductions in measured 2-nonenal and odor intensity after daily use of a soap containing a plant-polyphenol blend with astringent persimmon and tea extracts.
5. Goto T, Mimasu Y, Mimasu T. (2026).
History of Kakishibu—Before and After the Plastic Era.
In Traditional Knowledge for Green Innovation with Japanese Persimmon Tannin, Kakishibu.
This historical review describes traditional kakishibu use and documents the 1984 deodorizing experiments with astringent persimmon juice, later patented in 1991.
6. PubChem — 2-Nonenal.
U.S. National Library of Medicine / National Center for Biotechnology Information.
Used for physical-property information, including 2-nonenal being insoluble in water and soluble in fixed oils.
