Objective:

To review evidence on skin volatile organic compounds (VOCs) and how odor profiles vary with age, sex, and other biological factors.

Approach:

• Search and selection: The narrative review used systematic searches of PubMed/MEDLINE, Scopus, and Web of Science through May 2026. Of 487 records identified, 55 studies were included.
• Evidence assessment: Studies were assessed using five criteria covering sample size, analytical validation, confounding control, study design, and reporting. Median sample size was 35; 38% were rated high quality, 41% moderate, and 21% low.

Key Findings:

• Fatty acids were the most abundant chemical class; 3-methyl-2-hexenoic acid was identified as a characteristic axillary odorant.
• Infant profiles were dominated by acidic VOCs, including acetic and propionic acids, and lacked androgen-related compounds typical of adult axillary odor. Evidence was limited to four small studies.
• During puberty, androgen-mediated apocrine gland activation coincided with steroid VOCs, including androstenone and androstanol, and increased branched-chain fatty acids. These findings came from cross-sectional comparisons.
• Sex-related differences were reported consistently in 10 of 11 adequately sized studies comparing male and female profiles. Androstenone was detected in 65%–80% of males and 10%–25% of females; female profiles also varied with menstrual cycle phase.
• In older populations, 2-nonenal was reported as a characteristic odorant, with concentrations increasing after age 40 alongside changes in lipid peroxidation products. The proposed oxidative mechanism has not been directly established experimentally.
• Skin microorganisms were associated with conversion of glandular secretions into VOCs: Corynebacterium with 3-methyl-2-hexenoic acid and other fatty acids, Staphylococcus with aldehydes and alcohols, and Cutibacterium acnes with propionic acid and other VOCs.
• Disease-detection studies, including those involving diabetes and melanoma, were preliminary; most had fewer than 50 participants, cross-sectional designs, and no independent validation.

Interpretation:

The review describes age- and sex-associated patterns in skin odor and identifies glandular secretions and microbial metabolism as complementary contributors. The authors state that clinical applications remain preliminary and require further validation.

Limitations:

• Most studies were cross-sectional; only 14% enrolled more than 100 participants, and 26% controlled for at least three potential confounders.
• Only 14% used authentic chemical standards for definitive VOC identification.
• The evidence had limited ethnic representation and substantial variation in sampling and analytical methods, with insufficient longitudinal data.
• The review included only English-language literature; heterogeneity prevented meta-analysis, and quality assessment did not use a validated risk-of-bias instrument.

Conclusion:

The authors called for standardized analytical protocols, longitudinal studies, normative reference data, and rigorous validation before odor-based approaches move toward clinical use.

Sources:

• Journal of Cosmetic Dermatology