Effect of Deodorant Active Ingredients on Underarm Sweat Microbiome

Modern deodorant actives are superior to traditional organohalogen systems. 2 methyl 5-cyclohexylpentanol (SymDeo® B125) shows no negative impact on human axillary microbiota, while triclosan disrupts this balance. Can long-lasting deodorant efficacy be achieved without damaging human axillary microbiota?

Introduction

Body odor formation begins primarily with human sweat containing water, small amounts of protein and natural lipids. Natural skin microbiota breaks down proteins and lipids into molecules with low odor thresholds. These molecules include short-chain fatty acids such as 3-hydroxy-3-methyl-hexanoic acid (HMHA) or 3-methyl-2-hexenoic acid (3M2H); organosulfur compounds such as 3-mercapto-3-methyl-1-hexanol, as well as steroids such as androstenone.[1] Body odor management is generally achieved through three separate cosmetic technologies used individually or in combination: antiperspirants, odor masking agents, or deodorant actives. Deodorant actives eliminate malodor (deodorize) without using aluminum salts (antiperspirants), with minimal fragrance or fragrance-free (deodorants). The ideal deodorant according to consumers is one that provides long-lasting protection through the combined use of such actives with other technologies.[2] Deodorant actives generally exhibit antimicrobial properties. In this context, when modern actives are tested, triclosan—representing the traditional organohalogen (organochlorine) system used for many years—serves as the benchmark antimicrobial agent. In cosmetics, examples of non-organohalogen technologies include farnesol[3], triethyl citrate[4], or 2 methyl 5-cyclohexylpentanol (SymDeo® B125).[5,6,7] When examining the mechanisms by which deodorant actives prevent malodor, modern antimicrobial technologies typically target bacteria that cause malodor. However, while information regarding the actual effects of these compounds on natural axillary microbiota[8,9] remains limited, application of a newly developed ex vivo model has enabled new findings on the effects of deodorant actives on human axillary microbiota. This article compares modern and traditional deodorant actives used in cosmetics. As a first step, the readily biodegradable (manometric respiration test 79%/28 days) and patented active SymDeo® B125 was compared with triclosan; performance testing of the actives was conducted through two clinical olfactory assessments. As a second step, an ex vivo human axillary microbiota model provided deeper insight into natural microbiota composition.

Experimental Design

Two in-vivo clinical studies compared SymDeo® B125, triclosan applied to underarms, and untreated controls based on olfactory odor assessment test data obtained from underarms. Actives were applied using a pump spray. The 24-hour clinical study of SymDeo® B125 and triclosan was conducted by Dr. Schrader Institut in Holzminden, Germany. Olfactory odor assessment was performed on 20 subjects aged 29-63 years, with odor evaluation comparing the actives against each other and baseline in randomized, double-blind, paired tests. During a 10-day preparation period, subjects were permitted only unscented, non-antimicrobial soap; use of antiperspirants, deodorants, and other cosmetic products was prohibited. Clothing worn by subjects contained no perfumed detergent or fabric softener. In the study, odor score was defined on a 0-5 scale (0=no odor, 5=very strong odor); subjects required a minimum score of 3 to participate. Following the preparation period, subjects' underarms were washed without any product applied, and odor assessment was performed by trained experts at 6 and 24 hours (t0=no product applied). Half the subjects applied formula A (SymDeo® B125 spray) to their left underarms and formula B (triclosan spray) to their right underarms; the other half performed this procedure in reverse. Olfactory assessment was performed 6 and 24 hours after a single application (t1=single application). Following 24-hour assessment, subjects continued applying test products morning and evening for four days; odor assessment was repeated 6 and 24 hours after the final application (t11=11 total applications). A 48-hour clinical study with SymDeo® B125 and untreated control was conducted at Kosmoscience Ciência & Tecnologia Cosmética Ltda in Brazil. Deodorant efficacy of test products was assessed through sensory evaluation at 6, 24, and 48 hours after final application. The evaluation compared left and right underarms (product applied to left side, right underarm washed only, or vice versa). The test formula used was a simple alcoholic spray containing 0.3% SymDeo® B125. Olfactory testing was performed by three trained assessors according to the Sensory Olfactory Method (ASTM E1207-14). Evaluations were scored on a 10-point scale (0=no malodor, 10=extreme malodor); the study included 30 subjects aged 29-60 (average age 50 ± 9). Prior to the product application period, subjects used non-antibacterial soap for seven days for cleansing. Control for residual aluminum in the underarm was performed only in authorized subjects. Following controlled washing, test product (0.5g) was applied as a spray to one underarm; after application, subjects were instructed not to use any underarm products for 48 hours and to remain in their white cotton t-shirt until final assessment.

Human Axillary Microbiota Model:

The human axillary ex vivo microbiota model developed and validated by Symrise was conducted on fresh human perspiration from 8 healthy subjects aged 39-64 (average age 55 ± 9). Previously collected perspiration was aerated and mixed with deodorant active. Samples were then incubated under controlled conditions at 37°C and evaluated at baseline (0h) and at 24 hours. Microbial analysis was addressed in two different ways: 1) Microbial Load – Aerobic and Anaerobic Colony Forming Units (CFU) Petri dishes containing agar were inoculated aerobically with 100 μl diluted perspiration. They were incubated at 37°C for 48 hours under aerobic or anaerobic conditions; bacterial colony count was tested and calculated at least twice technically. 2) Microbiota Content – Bacterial Amplicon Sequencing (16S rRNA gene) Sequencing and bioinformatics evaluation were performed at CeMeT GmbH in Tübingen, Germany. DNA was isolated using the Qiagen MagAttract PowerSoil DNA Kit; PCR testing was performed on variable regions 3 and 4 of the 16S rRNA gene. Sequencing was evaluated using the MiSeq Reagent v3 (600 cycles) kit with 83.05% study quality achieved. Data were compared against the NCBI Bacteria 16S rRNA database and identified by species information. In all experiments, the 20 most abundant genes were selected.

Results: Clinical Study – Deodorant Efficacy Figure 1: (24-hour study)

Following subject evaluation, triclosan at single and multiple applications showed significant reduction in body odor (p≤0.05) compared to baseline (t0) at 6 and 24 hours. The same effect was observed in the test sample containing SymDeo® B125; only the 24-hour value after regular application did not create a significant difference compared to the initially determined baseline. In the evaluation section by study subjects, following multiple applications, 6-hour assessment showed significant difference for both test samples compared to baseline; the same can be stated for the 24-hour value for the triclosan sample. When test products (triclosan and SymDeo® B125) were compared with each other in this study, no significant difference in body odor was obtained. At 6 hours post-application, a 51.2% reduction in underarm malodor was observed. (At 24 hours 47.9% and at 48 hours 45.8%, respectively.) When the test product was compared to the untreated side, it provided statistically significant reduction in underarm odor (p≤0.05) at 6, 24, and 48 hours. All participants showed reduction in underarm malodor at all three time points. The strongest reduction was detected 6 hours after application.

Human Axillary Microbiota Model

Figure 3: Cell Growth Count As shown in Figure 3, untreated perspiration sample contained 107 CFU/mL microorganisms. There was equal distribution between aerobic and anaerobic microorganisms. When untreated perspiration sample was incubated under controlled conditions at 37°C (body temperature), aerobic cell levels were observed to increase to 108 CFU/mL. When the same conditions applied to perspiration sample treated with 0.1% triclosan and compared to untreated perspiration sample, significant reduction in live cell count was observed at 24 hours, negatively affected by triclosan. In contrast, perspiration sample treated with 0.1% SymDeo® B125 showed cell count at 24 hours nearly equal to the cell count in untreated perspiration sample. Consequently, while live cell count decreased significantly with triclosan (strong antimicrobial), it remained nearly unchanged with SymDeo® B125 use. Comparisons were made with perspiration sample containing no active. Evaluation of high-quantity live microorganisms advanced us further; detailed analysis through bacterial amplicon sequencing at 16S rRNA gene level on the diversity of different chains became possible. Detailed microbiota content is shown in Figure 4. Untreated perspiration sample, designated at hour 0 (0h), had a distribution dominated primarily by three genera of gram-positive bacteria: Staphylococcus, Anaerococcus, and Corynebacterium. Over 24 hours, untreated perspiration sample was incubated at 37°C (body temperature) and changes in bacterial composition were observed. Anaerococcus spp. and Peptoniphilus spp. quantities increased, Corynebacterium spp. quantity remained nearly unchanged, and Staphylococcus spp. quantity decreased. The 24-hour results of sample treated with 0.1% SymDeo® B125 were quite similar to untreated perspiration data; the 24-hour results of sample treated with 0.1% triclosan showed significant increase in gram-negative Pseudomonas quantity. Analysis showed that triclosan significantly affected and altered microbiota composition. Conversely, SymDeo® B125 showed minimal impact on microbiota composition and caused no significant changes.

Discussion

Table 3: Summary Results Comparison of traditional and modern deodorant actives. The two clinical studies presented yield two key findings. First, the 24-hour study demonstrates comparable deodorant efficacy of triclosan and SymDeo® B125. Both significantly reduced body odor compared to baseline values. Second, in the 48-hour study, SymDeo® B125 significantly reduced body odor compared to untreated underarm across all time periods. In terms of clinical efficacy, traditional and modern actives showed equal effectiveness in reducing malodor, and SymDeo® B125 provided long-lasting efficacy up to 48 hours. While traditional and modern formulations showed similar sensory properties, significant differences were observed at the microbiota level. The modern system (SymDeo® B125) demonstrated its advantage by showing minimal impact on natural axillary microbiota. As previously reported[12], eliminating all bacteria indiscriminately is unnecessary to achieve deodorant efficacy. Our hypothesis is that SymDeo B125 creates an inhibitory effect on microorganisms, preventing malodor development. This effect also demonstrated that SymDeo® B125 is a microbiota-friendly alternative to traditional organohalogen systems.

Conclusion

Modern cosmetic formulations can take advantage of the performance of long-lasting modern deodorant actives like SymDeo® B125 and do not need to rely on strong antimicrobial actives such as triclosan. This modern alternative provides formulators the opportunity to develop microbiota-friendly products without compromising efficacy. The original version of this article was published in English in Cosmetics & Toiletries Vol.135; No.4, 54-62; Mind Your Microbes; Gentle Malodor Protection Supports the Axillary Microbiome.

References

[1] Natsch, A. (2015). What Makes Us Smell: The Biochemistry of Body Odour and the Design of New Deodorant Ingredients, CHIMIA 69 414-420.

[2] Symrise AG: CMI Data Source, Symrise Cosmetic Ingredients consumer data base.

[3] Symrise AG (2019, Nov 11): Farnesol; Nature-identical sesquiterpene alcohol. Available at https://www.symselect.com/deodorants

[4] Niendorf, H. (2012, Sept). Natural deodorising active for modern formulations; Personal Care Magazine 39-42.

[5] Symrise AG (2019, Oct 11): SymDeo® B125; Patented highly effective deodorant active. Available at https://www.symselect.com/deodorants

[6] Pesaro, M., Diesing, B., Schmaus, G., Pillai, R. (2011, Dec). 2-Methyl 5-Cyclohexylpentanol: Development of a Novel Deodorant Agent; SOFW-Journal 137 61-68.

[7] Kuhn, W., Wöhrle, I., Dilk, I., Ewering, Ch., Mampel, J., Krohn, M., Zinke, H. (2009, Apr 28). EP2424829 B1, US8623340B2, BRPI0924661B1…. OMEGA-CYCLOHEXYLALKAN-1-OLES AND USE THEREOF AS ANTIMICROBIAL ACTIVES TO COMBAT BODY ODOR.

[8] US National Institutes of Health, Human Microbiome Project (2019, Oct 11): Available at https://hmpdacc.org/

[9] The Human Microbiome Project Consortium (2012) in Nature 486 (7402) 207-214 and 215-221.

[10] Nordzieke, S., Diesing, B., Singer, M., Wittlake, R., Lanfermann, I., Winkler, S., Schmaus, G., Pesaro, M., Koch, C. (2019). The Good, the Bad, and the Smelly – developing a representative model for the human axillary microbiome. Poster, Annual Conference of the Association for General and Applied Microbiology (Mainz, Germany).

[11] Nordzieke, S., Diesing, B., Singer, M., Wittlake, R., Lanfermann, I., Winkler, S., Schmaus, G., Pesaro, M., Koch, C. (2019). Going ex vivo – Applying a representative model for the human axillary microbiome. Poster, 25th IFSCC Conference on Cosmetic Science and Conscience (Milan, Italy).

[12] Haustein, U.-F., Herrmann, J., Hoppe, U., Engel, W., Sauermann, G. (1993). Growth inhibition of coryneform bacteria by a mixture of three natural products Farnesol, glyceryl monolaurate, and phenoxyethanol: HGQ. J. Soc. Cosmet. Chem. 44 211-220.

 

Compiled by: Tuğba Bayazıt

Technical Application Specialist, Africa, Middle East, Turkey Team Leader

Symrise

Authors:

Dr. Florian Genrich, Dr. Sabrina Behnke, Dr. Steffen Nordzieke, Dr. Christin Koch, Dr. Gerhard Schmaus