@phdthesis{5864603,
  abstract     = {{Why do armpits smell bad? Why do some of the clothes smell bad? What causes body odor? Is it good to wear deodorant or antiperspirant? Can we wash the odors and bacteria away? What can we do against body odor? These and many other questions are handled in the doctoral work “The Science of Body Odor – Characterization and Management of the Axillary Microbiome”. 
Body odor is created by the presence of the ‘wrong’ bacteria which can transform sweat secretions into volatile malodorous compounds. This research identified the main bacterial malodor perpetrators in the armpit and clothes. The axillary microbiome of over 300 people was investigated, where Staphylococcus spp. and Corynebacterium spp. represented the majority (79%) of the total axillary microbiome. The presence of Staphylococcus epidermidis spp. in the axillary region resulted in a better axillary odor. Corynebacterium spp. were identified as the main malodor culprits, next to a variety of other, low abundant, species. The axillary microbiome was quite stable over time, although small differences were seen between left and right armpit for half of the investigated people. Male armpits were characterized with more Corynebacterium spp. and less Staphylococcus spp. as compared to female armpits. The malodorous axillae instigated a strong psychological impact, resulting in a high repetitive behavior (washing and deodorant use) and significant social and functional impairment. Especially females had a higher sensitivity towards malodor. Axillary osmidrosis is a strongly underestimated taboo issue, affecting the quality of life of affected people on a daily basis. The usage of antiperspirants led to an enrichment of malodor-causing species which might lead to a more unpleasant axillary odor. The aluminum salts had a higher effect on the Staphylococcus spp. than on the Corynebacterium spp. The aluminum salts also cannot reach the apocrine sweat glands, which flow onto the hair root. Bacterial transformations of these apocrine sweat secretions lead to malodor. Overall, the use of deodorants and antiperspirants resulted in an increase of microbial diversity. Additionally, certain clothes were identified as a source of body odor. Polyester clothes smelled significantly less pleasant as compared to cotton T-shirts after an intensive 1h fitness session. The clothes developed their own microbiome which consisted mostly out of typical skin-related microbiota. Micrococci were isolated, detected and selectively enriched on the synthetic shirts and regarded partially responsible for the malodor generation. Laundering of the clothes resulted in a decrease in microbial counts, however, the same bacterial species were still present. Laundering resulted in a microbial selection of typical clothes- and skin-related bacteria on the washed textiles. Malodor-causing microbiota can consequently be further distributed to other laundered clothes. A good drying of the laundry and a frequent maintenance wash of the laundry machine can prevent this. 
This research investigated the potential of an armpit bacterial transplantation to improve the axillary odor. Axillary bacteria from people without body odor were harvested and transferred to the washed axillae of people who suffer from it. The armpit bacterial transplantation seemed successful between family members. An induced dominance of Staphylococcus spp. was obtained together with a decrease of Corynebacterium spp., with a subsequent improvement in axillary odor. Not only the bacterial transplant, but also the eradication of the autochthonous community by means of disinfectants and antibiotics and the specific enrichment of the Staphylococcus spp. by means of cotton pads resulted in an induced microbial shift towards Staphylococcus spp. An axillary therapy was proposed in this research, compressing the three steps, which caused an odor improvement on short (one month - 90%) and longer term (three months or longer - 50% of the treated people). Further research is necessary to obtain a lasting effect for all subjects. The proposed axillary therapy nevertheless forms a valuable alternative for the existing treatments against malodorous axillae. Additionally, an artificial sweat composition was created in this research which enabled high-throughput microbial, odor and chemical analysis on axillary odors. The sweat solution was able to grow and sustain mixed axillary microbiota and showed similar volatile organic compounds as in vivo axillary malodor components. Lastly, a novel sustained release system for the skin was developed for perfume molecules using PLA nanocapsules. The nanocapsules showed a slow and sustained release of fragrances on the skin, especially for hydrophobic compounds. For years, the idea was to kill off all bacteria to prevent malodors. The answer all along might have been the protection of the ‘right’ bacteria.}},
  author       = {{Callewaert, Chris}},
  isbn         = {{9789059897793}},
  keywords     = {{armpit bacterial transplantation,Body odor,armpit,bacteria,smelly,laundry machine,clothes}},
  language     = {{eng}},
  pages        = {{XII, 269}},
  publisher    = {{Ghent University. Faculty of Bioscience Engineering}},
  school       = {{Ghent University}},
  title        = {{The science of body odor : characterization and management of the axillary microbiome}},
  year         = {{2015}},
}