A Thai, double-blind, randomised controlled trial revealed that wearing socks coated with nanoparticles of zinc oxide led to less bromodosis and pitted keratolysis in military cadets during field training.
“While completing an internship as a naval officer in the medical department, I saw a high number of foot infections in military personnel. I wanted to find a way to prevent and treat these fungal and bacterial infections and those conditions associated,” Dr Punyawee Ongsri (Siriraj Piyamaharajkarun Hospital, Mahidol University, Thailand) explained the motivation for the presented study .
Metal oxides have shown antibacterial action for a wide range of bacteria, including antibiotic-resistant species. They act by generating reactive oxygen species that may destroy bacterial walls and, for example, induce bacterial DNA damage. “Antibacterial efficacy is determined by size and concentration of the particles,” stated Dr Ongsri. Previous studies have shown that several metal oxide particles like zinc, titanium, silver, or silica can have antibacterial effects and some are already used in different industrial fields. Special features of zinc oxide nanoparticles (ZnO-NP) are their photocatalyticity and the lack of evidence of environmental toxicity in contrast to, for example, silver oxide.
The double-blind, randomised controlled trial included more than 140 cadets of the Thai Naval Rating School, who took part in a 2-week field training course and had no history of bromodosis or abnormal foot lesions like pitted keratolysis. The cadets were provided with 2 pairs of either ZnO-NP-coated socks or uncoated socks. The groups were not statistically different in baseline characteristics.
Before the training, a self-assessment of foot odour and a dermatologic, intervention-blinded examination was performed along with the completion of a questionnaire on behavioural risk factors by the cadets. During training, the provided socks had to be worn ≥8 hours a day and the use of any foot treatment such as deodorant was not allowed. After the training, the same assessments followed.
The results showed significantly less cases of pitted keratolysis (15.7% vs 40.5%; P=0.05) and a reduction in foot odour (-0.34 vs -0.14; P=0.34; see Table). The ZnO-NP-coated socks were also associated with high satisfaction in use by the cadets compared with the uncoated socks (95.9% vs 83.8%; P=0.01). “Persons in the uncoated-sock group complained of a more intense foot odour, which had a moderate to large effect on their daily life,” stated Dr Ongsri. He concluded: “We propose that wearing these socks could be adopted as a primary prevention in populations at risk, especially in military personal.”
Table: Results after the 2-week field training course 
*Mann-Whitney U test; **unpaired t-test.
ZnO-NP, zinc oxide nanoparticles; VAS, visual analogue scale.
- Ongsri P, et al. Effectiveness and safety of zinc oxide nanoparticle-coated socks compared to uncoated socks for the prevention of unpleasant foot odour: A double-blinded, randomized, controlled trial study. FC05.05, EADV 2020 Virtual Congress, 29-31 Oct.
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