Topical application of an oil-in-water zinc oxide (ZnO) emulsion to the axillae reduces odour and improves wound healing, researchers reported on April 12 during the 2019 European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Amsterdam.
According to a press release, the research was conducted by Professor Magnus S. Ågren of Copenhagen Wound Healing Center, Bispebjerg Hospital, Copenhagen, Denmark, Khaled Saoud Ali Ghathian, Department of Clinical Microbiology, Hvidovre Hospital, Hvidovre, Denmark, and their colleagues.
The primary aim of the study was to see if repeated application of the ZnO emulsion reduced underarm odour in healthy volunteers. As well, the investigators examined the association with overall bacterial growth, and growth of Corynebacterium spp. and Staphylococcus hominis specifically. Also studied were skin surface pH and the anti-inflammatory and wound-healing effects of topical ZnO. The latter was assessed via the extent of skin erythema and keratin evolution in two standardized wound models: one inflicted by a contact-activated lancet producing small bleeding wounds and the other was induced by ablative CO2 laser producing dry erosions in the skin.
A total of 30 healthy volunteers—15 female and 15 male, mean age of 25.6 years—were included. Participants’ left and right axilla were randomized to ZnO application or placebo, and treated for 13 consecutive days with five visits to the hospital.
Participants were enrolled, swabbed and began treatment on day minus 8. Bacterial swabs were taken again on day 0, and wounds were inflicted on this visit as well. The participants were seen again on days 3, 4 and 5, and were asked on the last visit whether they had observed a difference in the odour from the left and right axillae and, if so, to state which axilla they judged superior with respect to odour.
The investigators found that treatment with ZnO reduced self-perceived bad odour compared with placebo. As well, overall bacterial growth and specifically the odour-generating Corynebacterium spp. and S. hominis swere significantly reduced with the active treatment despite increasing skin surface pH.
Topical ZnO also reduced peri-wound erythema around the lancet-induced wounds and promoted the formation of keratin.
The authors conclude: “Daily application of ZnO reduced malodour from the axilla and causative bacteria, increased skin surface pH and attenuated wound inflammation.”
In the press release, Professor Ågren said: “The most frequent response we had from participants was: ‘where can I buy this fantastic product?.’ Even though it contained no fragrance like conventional deodorants, the participants could identify that it had neutralized any bad odour under the arm where it was applied."
The research was sponsored by Colgate-Palmolive.
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