OLDER people don鈥檛 smell so bad 鈥� at least not those in the US. A study has found no evidence of chemicals previously blamed for an unpleasant 鈥渁geing odour鈥� in the skin secretions of Americans in their forties and above.
In 2001, researchers at cosmetic company 鈥榮 Product Development Center in Yokohama asked a group of Japanese men and women to sleep in T-shirts for three consecutive nights. The researchers then studied the volatile chemicals picked up by the material. Volunteers over 40 produced an unsaturated aldehyde called 2-nonenal, which the team described as having an unpleasant 鈥済reasy鈥� smell.
鈥淚 thought, I鈥檓 way older than some of these guys, and I don鈥檛 think I smell that bad! My wife would have told me a long time ago,鈥� jokes George Preti of the in Philadelphia, Pennsylvania, who led the new study with his colleague Michelle Gallagher.
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To investigate further, Preti and Gallagher asked 13 men and 12 women to walk up and down stairs for 5 minutes, and then placed glass funnels over their backs and forearms for the next 30 minutes. The funnels contained a fibre that absorbed a sample of the chemicals given off. To complete the picture, the researchers also swabbed the volunteers鈥� forearms and backs using an organic solvent, and analysed the compounds that this picked up.
There were some differences between older and younger volunteers. For instance, over-40s gave off more dimethylsulphone, which comes from the metabolism of sulphur-containing amino acids. However, this compound does not have a strong smell. What鈥檚 more, there was none of the foul-smelling chemical found by the Shiseido team (British Journal of Dermatology, ).
Why should older Americans smell better than ageing Japanese? 鈥淚 attribute it to diet,鈥� says Preti, who notes that the typical Japanese diet contains much more seafood. This would cause a build-up of unsaturated fatty acids over time, which can be oxidised to 2-nonenal and related compounds. The Japanese team also found that older people鈥檚 skin produced more lipid peroxides, which would accelerate this oxidation.
Even though Preti and Gallagher got their volunteers to use unscented soaps and shampoo for at least a week prior to the experiment, many of the chemicals they found came from cosmetic products 鈥� in particular residues from shampoos given off from the backs of the women. 鈥淕irls use these shampoos more than guys,鈥� says Gallagher. 鈥淚t鈥檚 not a true gender biomarker.鈥�
Preti and Gallagher are also studying odours given off by a form of skin cancer called basal cell carcinoma, to see if the way these differ from normal skin odours can be used to aid diagnosis.
