Human skin odor changes may represent patterns across the lifespan.
Investigators conducted a narrative review using systematic search methods to characterize skin volatile organic compounds (VOC) and their variations across age, sex, and other biological factors. They searched PubMed/MEDLINE, Scopus, and Web of Science through May 2026, yielding 487 records, 55 of which were included. The investigators assessed evidence using 5 criteria covering sample size, analytical validation, confounding control, study design, and reporting completeness. Among the included studies, 38% (n = 22) were rated high quality, 41% (n = 24) moderate quality, and 21% (n = 12) low quality; the median sample size was 35 participants.
Across the evidence base, fatty acids were the most abundant chemical class, with 3-methyl-2-hexenoic acid identified as a characteristic axillary odorant. Aldehydes, ketones, alcohols, and other compounds also contributed to odor profiles.
Age-related differences were apparent from infancy. Infant odor profiles were dominated by acidic VOCs, including acetic and propionic acids, and lacked androgen-related compounds characteristic of adult axillary odor. Evidence at this stage was limited to 4 studies with small sample sizes. During puberty, androgen-mediated apocrine gland activation coincided with the emergence of steroid VOCs, including androstenone and androstanol, and increased levels of branched-chain fatty acids such as 3-methyl-2-hexenoic acid. However, the investigators relied on cross-sectional comparison data.
Sex-related differences were most consistent during reproductive age. Among 11 studies directly comparing male and female VOC profiles with adequate sample sizes, 91% (n = 10) reported consistent sex-specific patterns. Concentrations of 3-methyl-2-hexenoic acid ranged from 0.5 to 2 μg per sample in males compared with 0.2 to 0.8 μg per sample in females. Androstenone was detected in 65% to 80% of males compared with 10% to 25% of females. Female profiles also showed variation associated with menstrual cycle phase.
In older populations, 2-nonenal emerged as a characteristic odorant that was absent or minimal in younger groups. Studies included in the review indicated that concentrations increased following age 40 years alongside changes in lipid peroxidation products. Six cross-sectional studies examining geriatric odor identified the emergence of 2-nonenal, but each involved 20 to 50 participants. The investigators noted that the proposed mechanism linking 2-nonenal to oxidative degradation of unsaturated fatty acids has not been directly established experimentally.
Skin microorganisms appeared to contribute to odor composition by converting glandular secretions into volatile compounds. Corynebacterium species were associated with production of 3-methyl-2-hexenoic acid and other volatile fatty acids, Staphylococcus species with aldehydes and alcohols, and Cutibacteriumacnes with propionic acid and other VOCs. Glandular secretion and microbial metabolism were complementary contributors to the skin odor profile rather than competing explanations.
Potential clinical applications included noninvasive disease detection and health monitoring, but the supporting evidence remained preliminary. Studies evaluated odor signatures associated with several conditions, including diabetes and melanoma, but most disease-detection studies enrolled fewer than 50 participants, used cross-sectional designs, and lacked independent validation. Control for potential influences such as diet, medication use, and hygiene was also inconsistent.
The review had several limitations. Most underlying studies were cross-sectional, only 14% of the studies enrolled more than 100 participants, and just 26% controlled for at least 3 potential confounders. About 14% used authentic chemical standards for definitive VOC identification. The investigators cited limited ethnic representation, substantial variation in sampling and analytical methods, and insufficient longitudinal evidence. The review was restricted to English-language literature, heterogeneity prevented quantitative meta-analysis, and quality assessment did not use a formal validated risk-of-bias instrument.
The investigators called for standardized analytical protocols, longitudinal studies, normative reference data, and rigorous validation before odor-based approaches can move toward clinical use.
“The field of human skin odor research is at a transformative stage, poised to transition from descriptive characterization to mechanistic understanding and clinical application,” wrote lead study author Ghada Farouk Mohammed, of the Department of Dermatology, Venereology, and Sexology, in the Faculty of Medicine at Suez Canal University in Egypt, and colleagues.
The study authors reported no conflicts of interest.
Source: Journal of Cosmetic Dermatology
