The phenomenon commonly known as “old people smell” refers to a distinct, often subtle scent associated with aging. It is a natural physiological occurrence, not an indication of poor hygiene. This unique body odor results from specific biochemical changes in the human body over time. It is a widespread phenomenon, even having a dedicated term in Japanese, “kareishu,” reflecting its recognition across different cultures.
The Molecule Behind the Scent
The primary chemical compound responsible for this distinct age-related scent is 2-nonenal. This unsaturated aldehyde is produced on the skin’s surface through lipid peroxidation. It forms when omega-7 unsaturated fatty acids, naturally present in skin lipids, undergo oxidative degradation.
Skin glands, particularly sebaceous glands, produce sebum, an oily substance containing these fatty acids. As individuals age, changes in skin composition and metabolism increase the levels of omega-7 fatty acids and other lipids on the skin. These lipids become more susceptible to oxidation, which breaks them down and leads to 2-nonenal formation. This continuous process results in 2-nonenal constantly evaporating from the skin’s surface as a volatile organic compound.
Why It’s More Noticeable with Age
The production of 2-nonenal becomes more noticeable with advancing age, typically starting around age 40 in both men and women. As the body ages, its natural antioxidant defenses decline, making skin lipids more vulnerable to oxidation. This reduced protection allows for a greater breakdown of fatty acids, resulting in increased 2-nonenal production.
Hormonal changes with aging, such as decreased androgen levels, can influence sebaceous gland activity and cellular turnover in the skin. While sebaceous gland activity may decrease in elderly women after menopause, sebum levels in men remain relatively unchanged until later in life, around age 80. Slower cellular turnover means oxidized fats and 2-nonenal linger on the skin longer, contributing to the scent’s persistent nature. Additionally, an individual’s own sense of smell can diminish with age, particularly after 70, which might affect their perception of their own body odor.
Addressing the Smell
Managing age-related scent involves understanding its origin in lipid oxidation on the skin. Since 2-nonenal is not water-soluble, traditional soaps may not effectively remove it, as they primarily target dirt and sweat. Specialized soaps containing ingredients like Japanese persimmon extract (tannins) are formulated to neutralize 2-nonenal by dissolving it or binding to the odor-causing compounds. These products can eliminate a significant percentage of 2-nonenal.
Beyond specific cleansing agents, maintaining overall skin health and hygiene can help. Regular bathing, exfoliating to remove dead skin cells, and applying moisturizers can improve skin condition. Wearing breathable fabrics, such as cotton, also helps, as these materials are less likely to trap body oils and sweat. For laundry, adding white vinegar or baking soda to the wash cycle can assist in removing odors from clothes and bedding that may absorb 2-nonenal.