On the scent trail - Deodorant specificity
13 April 2010
By Dr Nicholas Read
The axillae, or “underarms” as they are more commonly known, are often associated with the problem of body odour. There are several reasons why this is the case but one of the main causative factors is the large number of eccrine, apoeccrine and apocrine sweat glands found in this region of the body (Wilke et al. 2007). The apocrine sweat glands appear to be especially important (Troccaz et al. 2004). These glands open onto the hair canal and secrete an oily substance containing proteins, lipids and steroids (Wilke et al. 2007). The fluid secreted by the apocrine glands is initially odourless but includes a number of odour precursors (Troccaz et al. 2009). These precursors are converted into odorous compounds such as the steroidal compound 5-α-androst-16-en-3-one, the fatty acid (R)/(S)-3-hydroxy-3-methylhexanoic acid and the thiol 3-methyl 1-3-sulfanylhexan-1-ol (Decreau et al. 2003; Troccaz et al. 2009). The conversion of the odour precursors is mediated by the action of micro-organisms that are found within the axilla (Decreau et al. 2003).
Microflora of the underarm
The human axilla supports one of the highest densities of micro-organisms found on the surface of the skin (Jackman and Noble, 1983). The precise composition of the micro-organisms varies from one individual to another, though in general consists of staphylococci, micrococci, propionibacteria, aerobic coryneforms and the yeast genus Malessezia (Taylor et al. 2003). Analysis of odour production has revealed that different micro-organisms contribute to odour levels to varying degrees. Results indicate that there is a strong correlation between odour levels and aerobic coryneforms (Taylor et al. 2003; Rennie et al. 1991). Of these aerobic corynebacteria it appears that those with the ability to metabolise free fatty acids make the most significant contribution to odour production, whereas the non-free fatty acid metabolising corynebacteria make little or no contribution (Austin and Ellis, 2003; James et al. 2004).
Scattergun or direct hit?
Despite there being only certain strains of bacteria within the axilla that make a significant contribution to body odour, the deodorants currently on the market tend to contain rather unspecific antimicrobials such as ethanol, cosmocil and triclosan. These antimicrobials reduce the total number of underarm bacteria, including many of the non-odour-producing bacteria which it may be beneficial to keep.
There is therefore potential for the development of deodorants containing compounds which specifically target odour-producing bacteria, and leave the non-odour-producing bacteria alone. Possible approaches in the future may include the use of compounds which stop or reduce the metabolism of the odour-producing bacteria through inhibition of key enzymes. Enzymes to target may include the zinc-dependent aminoacyclase and C-S lyase described by Natsch et al. (2004), both of which have been shown to be involved in the release of odoriferous compounds from odourless axilla secretions. Other approaches may be to target the odour-producing bacteria through the use of antibodies raised against the odour producers (Casey et al. 2001) or through the limitation of nutrients specifically required by the odour producers (Landa and Makin, 2003).
Given that there is some evidence that cocci and corynebacteria are able to antagonise or outgrow each other (Jackman and Noble, 1983), it is probable that the competition from the non-odour formers will slow the re-establishment of the odour formers long after the antimicrobial is still active. From this it is possible that a more targeted antimicrobial approach may lead to a more sustained deodorising effect. Such an effect would clearly be attractive as it would have the potential to improve upon the performance of the deodorants currently on the market.
References
Wilke K., Martin A., Terstegen L. and Biel S. (2007) A short history of sweat gland biology. International Journal of Cosmetic Science 29, 169-179
Troccaz M., Starkenmann C., Niclass Y., van de Waal M. and Clark AJ. (2004) 3-methyl-3-sulfanylhexan-1-ol as a major descriptor for the human axilla-sweat odour profile. Chemistry and Biodiversity 1, 1022-1035
Troccaz M, Borchard G, Vuilleumier C, Raviot-Derrien S, Niclass Y, Beccucci S and Starkenmann C. (2009) Gender specific differences between the concentrations of non-volatile (R)/(S)-3-methyl-3-sulfanyl-1-ol and (R)/(S)-3-Hydroxy-3-methyl-hexanoic acid odor precursors in axillary secretions. Chemical Senses, advance access 1-7
Decréau RA, Marson CM, Smith KE, and Behan JM. (2003) Production of malodorous steroids from androsta-5,16-dienes and androsta-4, 16-dienes by Corynebacteria and other human axillary bacteria. Journal of Steroid Biochemistry and Molecular Biology 87, 327-336
Jackman PJH and Noble WC. (1983) Normal axillary skin microflora in various populations. Clinical and Experimental Dermatology 8, 259-268
Taylor D, Daulby A, Grimshaw S, James G, Mercer J. and Vaziri S (2003) Characterisation of the microflora of the human axilla. International Journal of Cosmetic Science 25, 137-145
Rennie PJ, Gower DB and Holland KT (1991) In-vitro and in-vivo studies of human axillary odour and the cutaneous microflora. British Journal of Dermatology 124, 596-602
Austin C and Ellis J (2003) Microbial pathways leading to steroidal malodour in the axilla. Journal of Steroid Biochemistry and Molecular Biology 87, 105-110
James AG, Casey J, Hyliands D and Mycock G (2004) Fatty acid metabolism by cutaneous bacteria and its role in axillary malodour. World Journal of Microbiology and Biotechnology 20, 787-793
Natsch A, Schmid J and Flachsmann F (2004) Identification of odoriferous sulfanylalkanols in human axilla secretions and their formation through cleavage of cysteine precursors by a C-S lyase isolated from axilla bacteria. Chemistry and Biodiversity 1, 1058-1072
Casey et al. (2001) United States Patent US 6,171,582 BI Method for preventing or reducing malodour
Landa AS and Makin SA (2003) Iron sequestration on skin: a new route to improved deodorancy. International Journal of Cosmetic Science 25, 127-135
The axillae, or “underarms” as they are more commonly known, are often associated with the problem of body odour. There are several reasons why this is the case but one of the main causative factors is the large number of eccrine, apoeccrine and apocrine sweat glands found in this region of the body (Wilke et al. 2007). The apocrine sweat glands appear to be especially important (Troccaz et al. 2004). These glands open onto the hair canal and secrete an oily substance containing proteins, lipids and steroids (Wilke et al. 2007). The fluid secreted by the apocrine glands is initially odourless but includes a number of odour precursors (Troccaz et al. 2009). These precursors are converted into odorous compounds such as the steroidal compound 5-α-androst-16-en-3-one, the fatty acid (R)/(S)-3-hydroxy-3-methylhexanoic acid and the thiol 3-methyl 1-3-sulfanylhexan-1-ol (Decreau et al. 2003; Troccaz et al. 2009). The conversion of the odour precursors is mediated by the action of micro-organisms that are found within the axilla (Decreau et al. 2003).
Microflora of the underarm
The human axilla supports one of the highest densities of micro-organisms found on the surface of the skin (Jackman and Noble, 1983). The precise composition of the micro-organisms varies from one individual to another, though in general consists of staphylococci, micrococci, propionibacteria, aerobic coryneforms and the yeast genus Malessezia (Taylor et al. 2003). Analysis of odour production has revealed that different micro-organisms contribute to odour levels to varying degrees. Results indicate that there is a strong correlation between odour levels and aerobic coryneforms (Taylor et al. 2003; Rennie et al. 1991). Of these aerobic corynebacteria it appears that those with the ability to metabolise free fatty acids make the most significant contribution to odour production, whereas the non-free fatty acid metabolising corynebacteria make little or no contribution (Austin and Ellis, 2003; James et al. 2004).
Scattergun or direct hit?
Despite there being only certain strains of bacteria within the axilla that make a significant contribution to body odour, the deodorants currently on the market tend to contain rather unspecific antimicrobials such as ethanol, cosmocil and triclosan. These antimicrobials reduce the total number of underarm bacteria, including many of the non-odour-producing bacteria which it may be beneficial to keep.
There is therefore potential for the development of deodorants containing compounds which specifically target odour-producing bacteria, and leave the non-odour-producing bacteria alone. Possible approaches in the future may include the use of compounds which stop or reduce the metabolism of the odour-producing bacteria through inhibition of key enzymes. Enzymes to target may include the zinc-dependent aminoacyclase and C-S lyase described by Natsch et al. (2004), both of which have been shown to be involved in the release of odoriferous compounds from odourless axilla secretions. Other approaches may be to target the odour-producing bacteria through the use of antibodies raised against the odour producers (Casey et al. 2001) or through the limitation of nutrients specifically required by the odour producers (Landa and Makin, 2003).
Given that there is some evidence that cocci and corynebacteria are able to antagonise or outgrow each other (Jackman and Noble, 1983), it is probable that the competition from the non-odour formers will slow the re-establishment of the odour formers long after the antimicrobial is still active. From this it is possible that a more targeted antimicrobial approach may lead to a more sustained deodorising effect. Such an effect would clearly be attractive as it would have the potential to improve upon the performance of the deodorants currently on the market.
References
Wilke K., Martin A., Terstegen L. and Biel S. (2007) A short history of sweat gland biology. International Journal of Cosmetic Science 29, 169-179
Troccaz M., Starkenmann C., Niclass Y., van de Waal M. and Clark AJ. (2004) 3-methyl-3-sulfanylhexan-1-ol as a major descriptor for the human axilla-sweat odour profile. Chemistry and Biodiversity 1, 1022-1035
Troccaz M, Borchard G, Vuilleumier C, Raviot-Derrien S, Niclass Y, Beccucci S and Starkenmann C. (2009) Gender specific differences between the concentrations of non-volatile (R)/(S)-3-methyl-3-sulfanyl-1-ol and (R)/(S)-3-Hydroxy-3-methyl-hexanoic acid odor precursors in axillary secretions. Chemical Senses, advance access 1-7
Decréau RA, Marson CM, Smith KE, and Behan JM. (2003) Production of malodorous steroids from androsta-5,16-dienes and androsta-4, 16-dienes by Corynebacteria and other human axillary bacteria. Journal of Steroid Biochemistry and Molecular Biology 87, 327-336
Jackman PJH and Noble WC. (1983) Normal axillary skin microflora in various populations. Clinical and Experimental Dermatology 8, 259-268
Taylor D, Daulby A, Grimshaw S, James G, Mercer J. and Vaziri S (2003) Characterisation of the microflora of the human axilla. International Journal of Cosmetic Science 25, 137-145
Rennie PJ, Gower DB and Holland KT (1991) In-vitro and in-vivo studies of human axillary odour and the cutaneous microflora. British Journal of Dermatology 124, 596-602
Austin C and Ellis J (2003) Microbial pathways leading to steroidal malodour in the axilla. Journal of Steroid Biochemistry and Molecular Biology 87, 105-110
James AG, Casey J, Hyliands D and Mycock G (2004) Fatty acid metabolism by cutaneous bacteria and its role in axillary malodour. World Journal of Microbiology and Biotechnology 20, 787-793
Natsch A, Schmid J and Flachsmann F (2004) Identification of odoriferous sulfanylalkanols in human axilla secretions and their formation through cleavage of cysteine precursors by a C-S lyase isolated from axilla bacteria. Chemistry and Biodiversity 1, 1058-1072
Casey et al. (2001) United States Patent US 6,171,582 BI Method for preventing or reducing malodour
Landa AS and Makin SA (2003) Iron sequestration on skin: a new route to improved deodorancy. International Journal of Cosmetic Science 25, 127-135