MALE GROOMING
Finally, recent immunohistochemistry studies suggest that sweat glands produce and excrete antimicrobial peptides such as dermcidin, cathelicidin, and lactoferrin pointing to a potential role of sweating in host defense against skin infection.9,10,11,12
Malodour formation on human axillary The moist environment of the human axilla is characterized by the presence of oily and odourless fluids containing proteins, cholesterol, steroid derivatives, squalene and a wide range of lipids.13
These substances are
secreted by eccrine, sebaceous and apocrine glands specifically located in the underarm region of the human body and some of which are stimulated by emotional stress.14,15 Emotional sweating does not occur
until puberty and is often associated with development of strong body odour.2
In the
past few decades, several studies have focused on the relationship between these odourless sweat secretions and the formation of a strong body odour. It has been known since the 1950s that the metabolic activity of microorganisms that inhabit the skin surface is essential for the development of body odour.2 Nevertheless, closer investigation of the
bacterial community structure in the axillary microenvironment showed that it is usually colonized by four major groups of bacteria, namely staphylococci, aerobic coryneforms, propionibacteria and micrococci.16
High
levels of strong body odour were observed in individuals with a microflora dominated by aerobic coryneforms, whereas staphylococci- dominated axillae only revealed low levels of odour.17 Until now, several routes of odour
formation have been detected including the transformation of glycerol and lactic acid, and the conversion of aliphatic amino acids into volatile fatty acids.18 Of all, the four routes most extensively studied and the generally accepted mechanisms are as follows: (i) the biotransformation of steroids, (ii) the release of short branched-chain fatty acids from glutamine-conjugates, (iii) the release of short sulfanylalkanols from glycine- cysteine- or cysteine-(S)-conjugates and (iv) the biotransformation of long-chain fatty acids into volatile short branched-chain fatty acids.1 It is now generally accepted that
Figure 3: Biotransformation of sweat and sebum O OH Figure 4: Structure of Caprylyl Glyceryl Ether
skin bacteria cause body odour by biotransformation of sweat and components secreted in the human axillae, especially aerobic corynebacteria have been shown to contribute strongly to axillary malodor. Analysis of odouriferous sweat components has shown that the major odour-causing substances in human sweat include steroid derivatives, short volatile branched-chain fatty acids, sulphanylalkanols and Diacetyl (2,3-butanedione)(Figure 2 & 3).1,19
Approaches to body odour control There are at least four formulation approaches
TABLE 1: MIC VALUES OF CAPRYLYL GLYCERYL ETHER AND ETHYLHEXYLGLYCERIN ON BACTERIA, INCLUDING BODY ODOUR RELATED BACTERIA STRAIN
MIC in ppm pH 7.0
Staphylococcus aureus (G+) Corynebacterium jeikeium (G+) Brevibacterium linens (G+) Corynebacterium xerosis (G+) Pseudomonas aeruginosa (G-) Escherichia coli (G-)
Enterobacter aerogenes (G-) Klebsiella pneumoniae (G-) Burkholderia cepacia (G-) Enterobacter gergoviae (G-) Citrobacter freundii (G-)
www.personalcaremagazine.com
Ethyhexylglycerin 1000 1000 1500 1000 >1000 7500
10000 500
3000
>10000 10000
Caprylyl Glyceryl Ether 500
1000 1500 1500
>10000 7500 3000 <250 750
>10000 5000
in creating cosmetic products targeting the body odour control. ■ Antiperspirants. This approach consists in formation of temporary plugs in the upper parts of the sweat pores by very acidic aluminum complexes. These antiperspirant substances also inhibit bacterial growth since they create acidic environment and reduce moisture in the axilla. ■ Antimicrobial deodorant agents. Second approach is to use molecules with antimicrobial activity and specific enzyme inhibition activity that specifically targets skin bacteria mainly Corynebacterium species involved in biotransformation of sweat, lipids and proteins into odourous substances, by reducing microbial count and their activity and metabolism. ■ Odour masking ingredients. The third strategy is odour-masking with efficient tailor- made fragrance compositions, incapsulated fragrances, essential oils and by using substances like clays, minerals and starches that could absorb moisture, sweat, sebum and odourous substances. ■ Fatty acids neutralizers. The fourth approach can involve efficient neutralization of short volatile fatty acids with alkaline ingredients like sodium bicarbonate and Magnesium minerals The optimal solution is based on the synergy of different molecules with multiple functions to
September 2022 PERSONAL CARE OH
BODY ODOUR
51
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