Skin Oils Start Producing 2-Nonenal From Age 40, Causing 'Old Person Smell'

Q: Why does the infamous age-related scent survive regular washing, and what hidden chemical makes it cling so stubbornly to your favorite clothes?

It survives regular washing because the age-related odor is driven by an oil-based, water-resistant compound that keeps being produced on the skin and readily sticks to fabric. The chemical most strongly linked to that smell is **2-nonenal**, an aldehyde formed when skin lipids and fatty acids oxidize as antioxidant defenses and skin repair decline with age. Unlike sweat and salt, 2-nonenal is **hydrophobic**, meaning it does not dissolve well in water. Experts say that makes an ordinary rinse or mild wash less effective. The molecule mixes with sebum and other body oils, then transfers into sweaters, pillowcases, sheets, towels and upholstery, where it can linger even after laundering. That is why a favorite sweater may smell “clean” at first but seem stale again once it dries. What remains is not dirt so much as **oily residue carrying 2-nonenal**, especially around collars, necklines and other skin-contact areas. Laundry habits can worsen this: cold water, overloaded machines, detergent residue and fabric softener can all leave oils behind or coat fibers so the odor stays trapped. Specialists stress this is a normal part of aging, not poor hygiene. While the science is not fully settled and other compounds may also play a role, 2-nonenal remains the leading explanation. Reducing it usually requires washing methods that target oils, such as enzyme detergents, warmer water when fabric allows, thorough rinsing, and frequent cleaning of clothes and bedding.

3 articles · Updated · The Guardian · Sep 3

A Japanese study detected 2-nonenal from age 40, linking the so-called “old person smell” to a normal age-related shift in body odor rather than poor hygiene.
Dermatologists say the compound forms when skin lipids change with age, then oxidize and break down as the skin’s protective capacity slows over time.
Levels vary widely by person, with genetics, microbiome, health, clothing, hygiene and environment all thought to influence how much 2-nonenal is produced and lingers.
A 2012 blind test of 41 young adults found odors from people aged 75 to 95 were rated less intense and less unpleasant than scents from younger groups.
Experts say regular bathing, laundry and airing rooms may reduce the smell, but no method stops 2-nonenal entirely and evidence for specialty soaps remains limited.