1Introduction
Zinc oxide (ZnO) has a dual mode of action against body odor. On skin contact it gradually solubilizes and releases zinc ions (Zn2+). These ions are bacteriostatic against the bacterial species responsible for axillary malodor, and they also interact with volatile odor molecules that are already present.
A randomized, double-blind, placebo-controlled clinical trial confirmed the antibacterial effect in vivo and a reduction in self-perceived malodor. Over 13 days of use, ZnO significantly reduced axillary Corynebacterium spp. colonization, attenuated the rise in S. hominis and reduced self-perceived malodor compared with placebo [1].
2How body odor forms
Fresh eccrine and apocrine sweat is essentially odorless. Apocrine glands in the axilla secrete odor precursors as odorless conjugates: branched-chain carboxylic acids bound to glutamine (Nα-acylglutamine conjugates), sulfur compounds bound to cysteine-glycine dipeptides, and steroids conjugated to glucuronic acid. These conjugates only become odorous once bacteria cleave them enzymatically [2,3].
The resident axillary microbiota is dominated by Corynebacterium spp., alongside Staphylococcus spp. and Cutibacterium spp., and expresses the enzymes that carry out this cleavage [4]:
- An Nα-acylglutamine aminoacylase releases volatile branched-chain fatty acids such as 3-methyl-2-hexenoic acid and 3-hydroxy-3-methylhexanoic acid. Among the axillary isolates tested, this enzyme was found specifically in Corynebacterium, which makes this genus the main driver of fatty-acid malodor [3,2].
- A separate dipeptidase / C–S β-lyase enzyme pair, attributed to Staphylococcus hominis, releases sulfanylalkanols such as 3-methyl-3-sulfanylhexan-1-ol. These are among the most potent odorants identified in human axillary secretions and have a sulfurous, onion-like character [4,2].
Because malodor is generated by bacterial enzymes and is not intrinsic to sweat, ingredients that reduce the abundance or metabolic activity of these species act upstream of odor formation. Masking agents and adsorbents act only on volatiles that have already formed.
3How zinc oxide works: a dual mode of action
3.1Release of zinc ions on skin
ZnO is only sparingly soluble in water at neutral pH. Axillary skin and sweat, however, provide a mildly acidic environment and organic acids that progressively hydrolyze the ZnO surface and release free Zn2+ ions:
ZnO(s) + 2H+(aq) → Zn2+(aq) + H2O
In a controlled clinical trial, a 1.1% w/w ZnO emulsion released approximately 1,450 mg/L of free Zn2+ into the aqueous phase of the formulation [1]. This pool of bioavailable zinc is the basis for the two effects described below.
3.2Bacteriostatic effect on odor-causing species
Released Zn2+ ions are bacteriostatic against the species directly involved in axillary malodor. In vitro susceptibility testing of Corynebacterium isolates from axillary samples found ZnO minimum inhibitory concentrations (MIC) of 3.2–400 mg/L, with minimum bactericidal concentrations (MBC) ≤ 10,000 mg/L for the majority of isolates tested. These concentrations are within reach of the Zn2+ levels generated on skin.
In the in vivo arm of the same trial, ZnO significantly reduced Corynebacterium spp. colonization (present at baseline in 63% of the 30 participants) and significantly attenuated the rise in S. hominis compared with placebo. These effects occurred even though ZnO raised, rather than lowered, skin-surface pH [1].
This is consistent with the broader antibacterial literature on zinc oxide. Released Zn2+ ions damage the bacterial cytoplasmic membrane and inhibit glycolytic enzymes by binding to their sulfhydryl groups. A secondary pathway involving reactive oxygen species has also been reported, but it is more typically associated with nanoparticulate ZnO under UV or metabolic activation [5]. On skin, at physiological pH and without significant photoactivation, ion release is considered the operative pathway.
3.3Odor complexation and passivation
Zn2+ also interacts directly with odor-active volatile molecules. Zinc ions have a well-characterized affinity for thiols and other sulfur-containing groups. In oral malodor research, zinc ions bound volatile sulfur compounds and suppressed their volatilization, in addition to a separate antibacterial effect on the odor-producing bacteria [6]. The same thiol chemistry is relevant to axillary sulfanylalkanols.
Complexation is also documented for zinc salts used as odor-control agents in cosmetics: molecular dynamics simulations of zinc ricinoleate show zinc adsorbing and neutralizing odor molecules [7], and anti-odor activity is an established functional category of zinc compounds in personal care [8].
Zinc salts deliver only the zinc that is available at the moment of application. ZnO particles that remain on the skin continue to solubilize in the mildly acidic axillary environment, so they act as a local zinc reservoir that supplies Zn2+ over time. For ZnO, odor passivation therefore works alongside the bacteriostatic effect: it acts on odor that is already present, while the bacteriostatic effect limits the formation of new odor.
4Clinical evidence
The main controlled clinical study of the axillary effects of ZnO was published in Acta Dermato-Venereologica [1]. Design and results:
- Design: 30 healthy volunteers (15 female, 15 male, aged 21–39). Each participant applied a 1.1% w/w ZnO emulsion to one axilla and a matched placebo to the other (contralateral, same-subject control), 0.5 mL daily for 13 days.
- Bacterial outcome: total retrievable bacteria were significantly lower on the ZnO-treated side than on the placebo side at Day 8 and Day 13 (p < 0.0005 at both time points). Corynebacterium spp. counts were also significantly lower than placebo (p = 0.020 at Day 8, p = 0.037 at Day 13). S. hominis rose on both sides over the study period, but the rise was significantly smaller on the ZnO-treated side (p < 0.0005 at Day 8, p = 0.012 at Day 13).
- Malodor outcome: self-perceived malodor was significantly lower on the ZnO-treated side (p = 0.005). Of the participants who could detect a difference between sides, the large majority rated the ZnO-treated axilla as less malodorous.
- Mechanistic support: in vitro testing of 19 Corynebacterium isolates cultured from the participants’ own baseline samples confirmed direct susceptibility to ZnO (MIC 3.2–400 mg/L) and showed that the antibacterial effect was not simply a pH artifact.
5Market context
Deodorant formulation is shifting away from aluminum salts, driven by demand for clean-label products and ingredient transparency. This creates room for actives such as ZnO that combine substantiated efficacy with a gentle, natural positioning.
- The aluminum-free deodorant market was valued at approximately USD 3.8–4.1 billion in 2025/2026 and is projected to reach USD 7.6 billion by 2034, growing at roughly 8.0% CAGR [9].
- Natural deodorants represent an estimated 18–19% share of the broader deodorant category, up roughly 7.6% year-over-year as of April 2026 [10].
- Over 70% of personal-care consumers cite ingredient transparency as an important purchase factor, and manufacturers increasingly pair aluminum-free claims with formulation narratives centered on the skin microbiome and skin biology [9].
- Among innovation trends tracked within natural deodorants, aluminum- and alcohol-free formulation ranks as a top-scoring driver, alongside eco-packaging and sustainability, and solutions for sensitive skin [10].
6Conclusion
Zinc oxide gives formulators a clinically substantiated route to body-odor control. Zinc ions released on skin act on the bacterial species responsible for malodor and also interact with odor molecules already present. This dual action addresses both the efficacy expectations and the clean-label demands that now shape deodorant innovation.
This white paper summarizes third-party published literature and publicly available market research alongside Uviva Technologies’ own product positioning. Customers building specific efficacy or marketing claims should confirm current substantiation requirements in their target markets and consult primary sources directly.
7References
- Ågren MS, Ghathian KSA, Frederiksen AKS, Bjerrum MJ, Calum H, Danielsen PL, Menon J, Hædersdal M, Jorgensen LN. Zinc Oxide Inhibits Axillary Colonization by Members of the Genus Corynebacterium and Attenuates Self-perceived Malodour: A Randomized, Double-blind, Placebo-controlled Trial. Acta Dermato-Venereologica 2020, 100(10), adv00145. doi.org/10.2340/00015555-3499
- James AG, Austin CJ, Cox DS, Taylor D, Calvert R. Microbiological and biochemical origins of human axillary odour. FEMS Microbiology Ecology 2013, 83(3), 527–540. doi.org/10.1111/1574-6941.12054
- Natsch A, Emter R. The specific biochemistry of human axilla odour formation viewed in an evolutionary context. Philosophical Transactions of the Royal Society B 2020, 375(1800), 20190269. doi.org/10.1098/rstb.2019.0269
- Khanna K. Microbial Origins of Body Odor. American Society for Microbiology (asm.org), published 30 December 2021.
- Mendes CR, Dilarri G, Forsan CF, et al. Antibacterial action and target mechanisms of zinc oxide nanoparticles against bacterial pathogens. Scientific Reports 2022, 12, 2658. doi.org/10.1038/s41598-022-06657-y
- Suzuki N, Nakano Y, Watanabe T, Yoneda M, Hirofuji T, Hanioka T. Two mechanisms of oral malodor inhibition by zinc ions. Journal of Applied Oral Science 2018, 26, e20170161. doi.org/10.1590/1678-7757-2017-0161
- Kuhn H, Fritzsche C, Bornscheuer U, Rehder W. Mechanism of the odor-adsorption effect of zinc ricinoleate. A molecular dynamics computer simulation. Journal of Surfactants and Detergents 2000, 3(3), 335–343.
- Abendrot M, Kalinowska-Lis U. Zinc-containing compounds for personal care applications. International Journal of Cosmetic Science 2018, 40(4), 319–327. doi.org/10.1111/ics.12463
- Straits Research (2026). Aluminum-Free Deodorant Market Size, Share & Growth Forecast, 2026–2034.
- Simporter (2026). Natural Deodorant Trends, April 2026 Market Data.
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The white paper is available as a PDF on request, including the figure with the clinical colonization data.