Botulinum Toxin-loaded Detachable Dissolvable Microneedles for Primary Axillary Hyperhidrosis: A Pilot Study on Efficacy and Safety

J Clin Aesthet Dermatol. 2025;18(1):E61–E66.

by Jidapa Triwatcharikorn, MD; Kridipop Charoenchaipiyakul, MD; Titiporn Sansureerungsikul; Nunthanach Chuenboonngarm, MD; Kornphaka Kantikosum, MD; Natcha Chottawornsak, MD; Bussabong Chancheewa, MD; Thanaporn Puaratanaarunkon, MD; Ratchathorn Panchaprateep, MD, PhD; Chanat Kumtornrut, MD, MSc; Puttikorn Pukfukdee, PhD; Supason Wanichwecharungruang, PhD; and Pravit Asawanonda, MD, DSc

Drs. Triwatcharikorn, Charoenchaipiyakul, Chuenboonngarm, Kantikosum, Chottawornsak, Chancheewa, Puaratanaarunkon, Panchaprateep, Kumtornrut, and Asawanonda are affiliated with the Division of Dermatology, Department of Medicine, Faculty of Medicine at Chulalongkorn University in Bangkok, Thailand. Dr. Kumtornrut is also affiliated with the Division of Dermatology, Department of Medicine, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, Thailand. Ms. Sansureerungsikul and Drs. Pukfukdee and Wanichwecharungruang are affiliated with the Department of Chemistry, Faculty of Science at Chulalongkorn University in Bangkok, Thailand.

FUNDING: This work was funded by the National Research Council of Thailand (809/2563) and the Center of Excellence in Advanced Materials and Biointerfaces, Chulalongkorn University.  

DISCLOSURES: The authors report no conflicts of interest relevant to the content of this article.

ABSTRACT: Objective: Botulinum toxin injection is a well-established treatment for primary hyperhidrosis. The botulinum toxin-loaded detachable dissolvable microneedles (BoNT-MNs) were developed in a result of disadvantages of the intradermal procedure. This pilot study aims to evaluate the efficacy and safety of BoNT-MNs.

Methods: This within-subject study included ten adults (N=10; 100% female) with mild primary axillary hyperhidrosis. BoNT-MNs patches were prepared and each microneedle patch contained 15 units of onabotulinum toxin. BoNT-MNs and placebo patches were randomly applied to different sides of axilla. Iodine-starch test, dermatologists’ and patients’ satisfaction scores were assessed at baseline and Weeks 1, 2, 3, 4, 8, 12, 16, 20, and 24.

Results: All ten female subjects completed the trial. Notably, on the BoNT-MNs side, iodine starch scores exhibited an onset at Week 2, with a 57.14-percent reduction at Week 12, returning to baseline after Week 20. Dermatologists’ and patients’ satisfaction scores were consistently superior to the placebo side from Week 2 and Week 1, respectively, until Week 16, with statistical significance (p<0.05) observed at Week 12 and Week 2.

Limitations: This study involved a limited number of female participants and administered a single, small dosage of botulinum toxin in the BoNT-MNs.

Conclusions: Botulinum toxin-loaded detachable dissolvable microneedles patches offer a safe and effective method for reducing axillary sweating.

Clinical trial: This study was approved by the Institutional Review Board of Faculty of Medicine, Chulalongkorn University with IRB number 567/63, and registered in the Thai Clinical Trials Registry (Thaiclinicaltrials.org) under registration number TCTR20201230002.

Keywords: Botulinum toxin, detachable dissolvable microneedles, hyperhidrosis, sweat, axilla

Botulinum toxin (BoNT) is FDA-approved for several conditions, including primary focal hyperhidrosis (PFHH).¹ Hyperhidrosis can be primary or secondary to certain etiologies.^2,3 Intradermal axillary botulinum toxin injection is an effective treatment, with varying doses of onabotulinumtoxin A from 50-100 units in each armpit.^4,5 Microneedling has been developed and is currently a promising mode of drug delivery.⁶ Therefore, we were interested in evaluating the efficacy of botulinum toxin-loaded, detachable, dissolvable microneedles for the treatment of primary axillary hyperhidrosis. 

Methods

This pilot study aimed to evaluate the efficacy and safety of botulinum toxin-loaded detachable dissolvable microneedles (BoNT-MNs) and was approved by the Institutional Review Board of Faculty of Medicine, Chulalongkorn University (IRB number 567/63). The clinical trial was registered in the Thai Clinical Trials Registry (TCTR20201230002). The study was conducted from February to July 2022. All subjects provided written consent for photographs taken and published.

Patient characteristics. Adult subjects, aged 18 to 60, were eligible. Inclusion criteria were subjects with Hyperhidrosis Disease Severity Scale (HDSS) 1. Exclusion criteria included patients with underlying diseases or on medications related to sweat gland functions, hyperhidrosis with HDSS 2–4,⁷ local infection, pregnancy, and allergy to product’s substances. Patients who had applied topical treatments for any conditions on the axillae or had received laser treatment to the areas within four weeks of the study were also excluded. Informed consent was obtained from all subjects. 

Study products preparation. BoNT-MNs patches were prepared by the Center of Excellence in Advanced Materials and Biointerfaces (CEMB, Chulalongkorn University, Thailand) under laminar flow, in a clean room and controlled environment (Biocontamination control, ISO 14698-1:2003 en), using the previously described process.⁸ The solution, comprising sodium hyaluronate (HA, Shandong Focuschem Biotech, China) and maltose (Sigma-Aldrich) were autoclaved at 121°C for 15 minutes. The sterile polymer solution was cooled down to 4°C and then mixed with onabotulinum toxin (Botox®, Allergan, Inc., Dublin, Ireland) under sterile condition at 4°C. The mixture was poured into sterile microneedle molds and the filled molds were kept in low humidity chamber (5% humidity) for two hours at 4°C. Then, wet sterile polyester fabric was placed firmly on the back of microneedle patches in the mold to allow the back of microneedles to integrate into the fabric. Afterwards, the fabric-assembled microneedle patches were left in moisture control chamber until completely dry. The dry microneedle patches were then removed from the molds, packed into foil pouches, and kept at 4°C. 

The placebo was 0.9% sodium chloride (NSS, Injection grade, Reg. no 1A 259/49, Pharma Innova Company, Thailand), otherwise prepared in exactly the same manner as BoNT-MNs. The microneedle patches were 70×20 millimeters rectangular patches, containing 900 microneedles. Each needle has 300×300μm square base column with height of 450 μm and 300×300 μm square base pyramid tips with height of 350 μm. These patches were loaded with approximately 15±1.5 units of onabotulinum toxin per 14 cm².

Treatment protocol. All subjects’ axillae were randomized for BoNT-MNs and placebo. The Iodine-starch test was used to assess HDSS, then photographed. Prior to patch applications, both axillae were cleaned with 70% alcohol. BoNT-MNs and placebo patches were placed on each side for two minutes. The iodine-starch test process was performed for re-evaluation after the BoNT-MNs and placebo patch application procedures. The patches were applied once. The use of antiperspirants, deodorants, and lasers were not allowed during the study. 

Clinical evaluation. Digital photography at baseline and nine follow-up visits (Weeks 1, 2, 3, 4, 8, 12, 16, 20,  and 24), was used for primary outcome assessment.   

The primary outcome was evaluated by two board-certified dermatologists (PA, CK) to assess changes using the previously reported score system based on the iodine-starch test, which ranged from 0 to 5.⁹ The secondary outcomes were dermatologists’ satisfaction scores and patients’ satisfaction scores (PSS), as follows: grade 0=unsatisfied, grade 1=fair, grade 2=satisfied, grade 3=very satisfied. Pain scores were evaluated by subjects during the first visit after patch application using visual analog scale, which ranged from 0 to 10. Adverse effects, including erythema, edema, tenderness, itching, and burning sensation, were also assessed. 

Statistical analysis. Age and pain score were reported as median and interquartile range, while gender and adverse effects were reported as frequency and percentage. The final scores of Iodine-starch scores and dermatologist satisfaction scores were calculated by mean scores from two raters. The interclass correlation coefficients (ICC) with a two-way random effect model to identify the inter-rater reliability of photographic iodine-starch test assessment and dermatologists’ satisfaction scores were used.¹⁰ 

The iodine starch scores, dermatologists’ satisfaction scores, and PSS between BoNT-MNs treated side and the placebo side were presented as mean, standard deviation, median, and Interquartile range. Differences in scores between groups were analyzed using Wilcoxon signed test. Changes of the scores over period were evaluated by Friedman test. A p-value of <0.05 was considered statistically significant. All data were analyzed using Stata 15.1 software (StataCorp LLC, College Station, TX, USA). Graphs were created by RStudio 4.3.1 software (R Foundation for Statistical Computing, Vienna, Austria).

Results

Patient characteristics. A total of 10 healthy female subjects with HDSS 1 were included in this study. The median age of the subjects (IQR) was 37.5 years (36, 40.75) (Table 1).

Clinical outcomes. The inter-rater reliability of iodine-starch test assessment and dermatologists’ satisfaction scores used in this study were verified and shown by intraclass correlation coefficients. The dermatologist’s photographic assessments were done independently. The summary of iodine-starch scores, dermatologists’ satisfaction scores, and PSS of both BoNT-MNs treated and placebo sides are shown in Tables 2–4.

The ICC for the assessment of the iodine-starch test and dermatologists’ satisfaction scores were both 0.98 (95%CI: 0.97–0.98 and 95% CI: 0.98–0.99, respectively)

Iodine-starch test assessment. Initially, baseline iodine-starch scores were higher on BoNT-MNs side, then declined by Week 2. In contrast, a decline from baseline in the placebo side was observed at Week 3. The scores on BoNT-MNs side showed a notably decrease of 57.14 percent from baseline by Week 12; however, the difference in scores did not achieve statistical significance. Long-term follow-up revealed scores on both sides returned to baseline values by Week 24 (Figure1A). The decrements in iodine-starch scores were obviously seen in representative cases (Figure 2).

Dermatologists’ satisfaction scores. Both dermatologists concurred on the reduction of iodine-starch test on BoNT-MNs side, with consistently higher satisfaction scores from Week 2 to Week 20. The BonT-MNs side outperformed the placebo side at most visits, reaching its peak between Weeks 12 to 20. Statistical significance was noted at Week 12 (p=0.0313). Scores on both sides declined by Week 24 (Figure1B).

Patients’ satisfaction scores. Subjects reported reduced sweating and increased satisfaction scores on both sides from the first follow-up week. Mean PSS on the BoNT-MNs side surpassed that of the placebo side in most visits, especially at Week 2, with statistical significance observed (p=0.0313). PSS on both sides converged to similar levels by Weeks 20 and 24 (Figure1C).

Adverse events. The adverse events, including erythema, edema, and burning sensation, were reported immediately following the microneedling procedure during the first visit. None of subjects developed itch. The side effects were transient and spontaneously resolved within a few days. The median pain scores were slightly higher on the BoNT-MNs side (2.5, IQR 2, 5) compared to the placebo side (2, IQR 1, 4). The values showed no statistically significant difference between both sides (Table 5).

Discussion

BoNT-A has been used for various medical disorders as well as axillary hyperhidrosis. The primary studies in 1996 reported the minimal dose to achieve anhidrosis was 50 units of BoNT-A with 2 to 3mL of normal saline dilution subcutaneously injection per axilla.¹¹ The anhidrosis persisted for eight months. Across several studies, the anhidrosis in axillae had onset within 7 to 10 days, and duration of 4 to 10 months.^12–14

To deliver the toxin to such depth within the skin where sweat glands are located, without needles, presents a challenge. This pilot study is the first experimental study to evaluate the efficacy and safety of BoNT-MNs for primary axilla hyperhidrosis. It is, of course, not our intent to “reproduce” the results of intradermal injections. We, however, demonstrated that this modality was, at least, first proof-of-concept that this novel intervention was effective for primary axillary hyperhidrosis.

Considering our assumption regarding the outcomes of iodine-starch test, dermatologists’ and PSS, we assume that BoNT-MNs begin its effect in the first week, lasting over 20 weeks and gradually diminishing after Week 24, similar to the original intradermal method. All results align with this assumption, showing an onset during the first to second week and a peak effect at Week 12, lasting until Week 16 to 20. Furthermore, PSS reached it peaks during the initial three weeks and gradually declined, in contrast to other parameters, reflecting that the patients were primarily able to perceive the rapid change at the onset.

Contrary to the procedural approach, we advocate the role of this approach as “at-home, less-painful, self” application, which could enable more frequent, albeit gradual, antiperspirant effects. Despite the lower dosage, all scores on BoNT-MNs were more satisfying than those on the placebo side. This highlights the capacity of BoNT-MNs to retain the toxin.

Our graphic illustration showed that the trendlines aligned in the same direction on both sides throughout the 24-week follow-up period. This alignment might be attributed to environmental temperature changes paralleling seasonal variation, potentially altering the results. It is obvious that climate plays a significant role in sweat production, especially in the tropics. According to literature reviews, seasonal acclimatization to humid heat enhances eccrine sweat gland function, leading to a higher whole body sweat during summer than in winter in hot-humid environments as a response to thermal stimuli.^15–17 During weeks 2 to 4 (2nd–16th February), the temperatures in Thailand were, on average, at their lowest annually (local temperature: 20–29°C). This resulted in an unexpected decrease in iodine-starch scores. Then sweat gland function returned at Week 4 (local temperature: 28–36°C). Not only seasonal changes but also individual variation, such as psychological stress, affect sweat rates through adrenergic and cholinergic activation.¹⁸

Since the degree of sweating declined on both sides, albeit to different degrees, several possibilities could be postulated. Micro-trauma to sweat glands from the microneedling procedure is most likely.¹⁹ Also, marginal decreases in sweating have been reported on the placebo side when botulinum toxin was injected to one armpit in previous studies,²⁰ which supports the observation of an initial surge in the effect on both sides during the first three weeks. Overall, patients reported higher satisfaction scores on BoNT-MNs side. Nevertheless, the degree of sweating may fluctuate depending on circumstantial temperature and emotional transition at different time points as stated. The graphs of iodine-starch scores, dermatologists’ satisfaction scores, and PSS indicate the duration of the effect with a reasonable tendency.

In our observation, some subjects noticed that their basal body temperature subjectively decreased during the menstrual phase. Corresponding to Kolka, and Stephenson, statistically significant differences in basal body temperature and sweating rate increased during the luteal phase in comparison to the follicular phase (p<0.05).^21-23 Therefore, fluctuations in both iodine-starch test and PSS might have occurred during the pre- and post-menstrual periods. The iodine-starch test darkened during luteal phase and became lighter during the menstrual phase as displayed in a sample case (Figure 3).

In this study, the adverse effects, including erythema, edema, tenderness, and burning sensation, were mild and spontaneously resolved. The self-assessed pain scores on the BoNT-MNs side were higher than on the placebo side, consistent with the findings of Kranz et al,²⁴ which described the local pain associated with needle penetration, volume suppression, and the interaction between injected substance and dermal tissue. The score was slightly lower than the study of Vadoud-Seyedi et al,²⁵ reporting mean pain score of 4.75 ± 2.40 after intracutaneous injection of BoNT-A with saline dilution. They also revealed that BoNT-A diluted in normal saline and BoNT-A diluted in lidocaine were similarly effective in terms of onset, duration of effect and subjective assessment of sweating. Henceforth, botulinum toxin-loaded detachable dissolvable microneedles diluted in lidocaine will be a developmental material for the next study. 

Limitations. The primary strength of our study was a within-subject design and a homogenous participant group. However, it had limitations, including the use of a suboptimal dosage of botulinum toxin, a small number of participants, and exclusivity to a female group due to the difficulty in recruiting male subjects willing to undergo hair removal. It is recommended that future studies include a larger participant size, include male subjects, and explore the effects with different dosages of botulinum toxin.

Conclusion 

BoNT-MNs offer a safe and effective method for reducing axillary sweating. The onset of the effect began within the second week, similar to that of traditional injections. Typical transient adverse effects included erythema, edema, and burning at the local application area. Pain scores on the BoNT-MNs side were slightly higher than on the placebo side but lower than that of the usual injection technique.

Acknowledgements

This study was supported by the National Research Council of Thailand and the Center of Excellence in Advanced Materials and Biointerfaces, Chulalongkorn University.  

References 

1. Lew MF. Review of the FDA-approved uses of botulinum toxins, including data suggesting efficacy in pain reduction. Clin J Pain. 2002;18(6 Suppl):S142–S146.
2. Vorkamp T, Foo FJ, Khan S, et al. Hyperhidrosis: evolving concepts and a comprehensive review. Surgeon. 2010;8(5):287–292.
3. Trindade De Almeida AR, Secco LC, Carruthers A. Handling botulinum toxins: an updated literature review. Dermatol Surg. 2011;37(11):1553–1565.
4. Obed D, Salim M, Bingoel AS, et al. Botulinum toxin versus placebo: a meta-analysis of treatment and quality-of-life outcomes for hyperhidrosis. Aesthetic Plast Surg. 2021;45(4):1783–1791.
5. de Almeida AR, Montagner S. Botulinum toxin for axillary hyperhidrosis. Dermatol Clin. 2014;32(4):495–504.
6. Henry S, McAllister DV, Allen MG, et al. Microfabricated microneedles: a novel approach to transdermal drug delivery. [published correction appears in J Pharm Sci 1998 Sep;88(9):948]. J Pharm Sci. 1998;87(8):922–925.
7. Kowalski J W, Eadie N, Dagget S, et al. Validity and reliability of the hyperhidrosis disease severity scale (HDSS) 1. J Am Acad Dermatol. 2004;50(3):51.
8. Pukfukdee P, Banlunara W, Rutwaree T, et al. Solid composite material for delivering viable cells into skin tissues via detachable dissolvable microneedles. ACS Appli Bio Mater. 2020;3(7):4581–4589.
9. Hexsel D, Rodrigues TC, Soirefmann M, et al. Recommendations for performing and evaluating the results of the minor test according to a sweating intensity visual scale. Dermatol Surg. 2010;36(1):120–122.
10. Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. [published correction appears in J Chiropr Med. 2017 Dec;16(4):346]. J Chiropr Med. 2016;15(2):155–163.
11. Bushara KO, Park DM, Jones JC, et al. Botulinum toxin–a possible new treatment for axillary hyperhidrosis. Clin Exp Dermatol. 1996;21(4):276–278.
12. Naumann M, Lowe NJ. Botulinum toxin type A in treatment of bilateral primary axillary hyperhidrosis: randomised, parallel group, double blind, placebo controlled trial. BMJ. 2001;323(7313):596–599.
13. Heckmann M, Ceballos-Baumann AO, Plewig G. Botulinum toxin A for axillary hyperhidrosis (excessive sweating). New Engl J Med. 2001;344(7):488–493.
14. Naumann M, Hofmann U, Bergmann I, et al. Focal hyperhidrosis: effective treatment with intracutaneous botulinum toxin. Arch Dermatol. 1998;134(3):301–304.
15. Lei TH, Fujiwara M, Gerrett N, et al. The effect of seasonal acclimatization on whole body heat loss response during exercise in a hot humid environment with different air velocity.  J Appl Physiol (1985). 2021;131(2):520–531.
16. Lee JB, Kim TW, Min YK, et al. Seasonal acclimatization in summer versus winter to changes in the sweating response during passive heating in Korean young adult men. Korean J Physiol Pharmacol. 2015;19(1):9–14.
17. Cage GW, Dobson RL. Sodium secretion and reabsorption in the human eccrine sweat gland. J Clin Invest. 1965;44(7):1270–1276. 
18. Harker M. Psychological sweating: a systematic review focused on aetiology and cutaneous response. Skin Pharmacol Physiol. 2013;26(2):92–100.
19. Chia KY, Tey HL. Approach to hypohidrosis. J Eur Acad Dermatol Venereol. 2013;27(7):799–804.
20. Lowe NJ, Glaser DA, Eadie N, et al. Botulinum toxin type A in the treatment of primary axillary hyperhidrosis: a 52-week multicenter double-blind, randomized, placebo-controlled study of efficacy and safety. J Am Acad Dermatol. 2007;56(4):604–611.
21. Kolka MA, Stephenson LA. Control of sweating during the human menstrual cycle. Eur J Appl Physiol Occup Physiol. 1989;58(8):890–895.
22. Lee H, Petrofsky J, Shah N, et al. Higher sweating rate and skin blood flow during the luteal phase of the menstrual cycle. Tohoku J Exp Med. 2014;234(2):117–122.
23. Garcia AM, Lacerda MG, Fonseca IA, et al. Luteal phase of the menstrual cycle increases sweating rate during exercise. Braz J Med Biol Res. 2006;39(9):1255–1261.
24. Kranz G, Sycha T, Voller B, et al. Pain sensation during intradermal injections of three different botulinum toxin preparations in different doses and dilutions. Dermatol Surg. 2006;32(7):886–890.
25. Vadoud-Seyedi J, Simonart T. Treatment of axillary hyperhidrosis with botulinum toxin type A reconstituted in lidocaine or in normal saline: a randomized, side-by-side, double-blind study. Br J Dermatol. 2007;156(5):986–989.