2-Nonenal
2-Nonenal is an unsaturated aldehyde (CAS: 2463-53-8; MW: 140.22)[1] which some research has associated with human body odor alterations during aging.
In the April 2001 issue of the Journal of Investigative Dermatology, Shinichiro Haze et al published an article entitled: "2-Nonenal, Newly Found in Human Body Odor Tends to Increase with Aging". [2]
In this article they reported on their work which involved the analysis of body odor components collected, via headspace gas chromatography/mass spectrometry, from shirts worn for 3 days by subjects between the ages of 26 and 75 . They found that the concentration of many components of body odor were unaffected by age. However, they did find that the concentration of 2-nonenal tended to increase with the age of the subjects. Furthermore, they determined that that 2-nonenal is generated by the oxidative degradation of omega-7 unsaturated fatty acids, such as palmitoleic acid and vaccenic acid, found on the skin surface.
They analyzed concentrations of various lipids on the skin surface by collecting samples in a gauze pad sewn into the shirts and then extracting the lipids with a hexane solvent. The article reported that concentrations of omega-10 fatty acids such as sapienic acid showed no change with age. However, concentrations of omega-7 fatty acids do increase with age.
2-Nonenal has an unpleasant greasy and grassy odor. Because of these findings, some observers have concluded that Haze's team has identified the cause of the phenomenon commonly known as "old lady smell", "old man smell" or "old person smell", an odor that is characteristically associated with the elderly.[3]
Old Person Smell also refers to a meme found in pop culture.