Research
Botulinum Toxin for Hyperhidrosis: The Evidence
Botulinum toxin type A is one of the best-studied treatments for focal hyperhidrosis. In a landmark placebo-controlled trial of 320 people with underarm (axillary) hyperhidrosis, 94% of those injected had at least a 50% reduction in sweating at 4 weeks, versus 36% on placebo, and mean sweat production fell by about 83%. A single treatment typically lasts several months (pooled estimates roughly 3 to 7 months). It works by blocking the nerve signal that switches on sweat glands. This page summarizes the verified clinical evidence for underarm, palm, and sole treatment. It is educational information, not medical advice.
By the Sweat Explained Editorial Team · Published 2026-07-13 · Last reviewed 2026-07-13 · Educational information, not medical advice.
Key statistics at a glance
94% vs 36%
of patients with at least a 50% reduction in underarm sweating at 4 weeks (botulinum toxin vs placebo)
Naumann & Lowe 2001, BMJ (N=320)
82% vs 21%
still responding at 16 weeks (botulinum toxin vs placebo)
Naumann & Lowe 2001, BMJ
~83%
mean reduction in underarm sweat production at 4 weeks
Naumann & Lowe 2001, BMJ
~3–7 months
typical duration of one underarm treatment before re-injection (pooled)
Meta-analysis, 12 RCTs / 904 patients
FDA-approved
for severe underarm hyperhidrosis (50 Units per axilla); palm/sole use is off-label
FDA BOTOX label (DailyMed)
How botulinum toxin reduces sweating
Sweat glands are switched on by the neurotransmitter acetylcholine, released from small sympathetic nerve endings in the skin. Botulinum toxin type A (marketed as products such as onabotulinumtoxinA) blocks the release of acetylcholine at those nerve endings (a process called chemodenervation) so the treated sweat glands are no longer stimulated. The drug is injected in a grid of small intradermal doses across the affected area.
The effect is temporary. Nerve terminals gradually recover and regrow, so sweating returns over several months and repeat injections are needed to maintain the result. Botulinum toxin reduces sweating in the treated area; it does not change the underlying tendency to sweat.
Underarm evidence: the placebo-controlled trial
The pivotal evidence comes from a multicentre, randomised, double-blind, placebo-controlled trial by Naumann and Lowe (BMJ, 2001) in 320 adults with bilateral primary axillary hyperhidrosis (242 received 50 Units of botulinum toxin type A per axilla; 78 received placebo). "Response" means at least a 50% reduction from baseline in sweat production, measured by gravimetry.
The gap between drug and placebo was large and sustained: 94% versus 36% responding at 4 weeks, and still 82% versus 21% at 16 weeks.
| Group | Value |
|---|---|
| Week 4, botulinum toxin | 94% |
| Week 4, placebo | 36% |
| Week 16, botulinum toxin | 82% |
| Week 16, placebo | 21% |
Source: Naumann M, Lowe NJ. BMJ 2001;323:596–599. Chart is an original rendering of the cited data.
How much it reduces sweat, and for how long
Beyond the responder rates, the same trial measured the size of the effect: mean underarm sweat production fell by about 83.5% at 4 weeks in the treated group, compared with about 20.8% on placebo. At 16 weeks the reduction was still roughly 69% versus about 4% on placebo.
Duration varies between people and studies. A meta-analysis of 12 randomised trials (904 patients) found the maintenance effect of an underarm treatment reported at roughly 14 to 31 weeks (about 3 to 7 months), with the authors noting that few studies tracked long-term duration. Some research also suggests the effect may last longer after repeated injections than after the first one.
Evidence by treatment site
Botulinum toxin has been studied for underarms, palms, and soles. Underarm use is FDA-approved; palm and sole use is common but off-label (used outside the specific approved indication). The figures below are from verified trials and systematic reviews.
| Area | Approval status | Efficacy / duration (verified) | Source |
|---|---|---|---|
| Underarms (axillary) | FDA-approved | 94% response at 4 wk vs 36% placebo; ~83% mean sweat reduction; lasts ~3–7 months | Naumann 2001; meta-analysis |
| Palms (palmar) | Off-label | Systematic review of 19 studies: mean duration ~4.9–9.5 months (weighted ~6.2); recurrence 61.5% by 3 mo, 80.8% by 6 mo | Front Med 2026 review |
| Soles (plantar) | Off-label | Less studied than palms/underarms; used similarly, with the same temporary, repeat-dose pattern | See reviews |
"Off-label" means the treatment is used outside the specific indication the FDA approved; it does not mean unstudied. Percentages come from different trials and populations and are not directly comparable.
Palms and soles: effective but more uncomfortable
For palmar (hand) hyperhidrosis, a 2026 systematic review of 19 studies reported a mean duration of effect of roughly 4.9 to 9.5 months for botulinum toxin type A (weighted mean about 6.2 months), with symptom recurrence in about 61.5% of patients by 3 months and 80.8% by 6 months. Quality-of-life scores improved substantially and reported satisfaction ranged widely (about 65% to 100%).
The main practical drawback of hand and foot treatment is discomfort: the palms and soles are sensitive, so injections there are more painful than in the underarms and often require local pain-management measures such as nerve blocks. Temporary weakness or reduced grip in small hand muscles has also been reported after palmar injection, because the toxin can affect nearby muscle. These are recognized considerations to discuss with a clinician, not reasons the treatment does not work.
Safety, side effects, and approval status
In the underarm trial, botulinum toxin was described as effective and well tolerated. Label-listed adverse reactions for underarm treatment include injection-site pain and bleeding, non-underarm (compensatory) sweating, and flu-like symptoms. As a class, all botulinum toxin products carry a boxed warning that the toxin's effect can, rarely, spread beyond the injection site; the FDA notes that no definitive serious spread-of-effect reports have occurred with the approved underarm dose (100 Units total).
The FDA-approved indication is severe primary axillary hyperhidrosis that is inadequately managed with topical agents, at 50 Units per axilla (100 Units total). Palm and sole treatment is widely used but off-label. Anyone considering botulinum toxin should discuss suitability, timing, and side effects with a qualified clinician; this page is educational information only and not a treatment recommendation.
Methodology and limitations
This page draws on primary randomised controlled trial data (Naumann & Lowe, BMJ 2001), a meta-analysis of 12 randomised trials (904 patients), a 2026 systematic review of palmar treatment (19 studies), and the FDA prescribing label via DailyMed. Each headline figure was traced to and confirmed on its source.
Limitations: efficacy and duration figures come from different studies with different populations, doses, follow-up lengths, and definitions of 'response,' so numbers across sites (underarm vs palm vs sole) are not directly comparable. Reported duration of effect varies widely between individuals. Palm and sole use is off-label. Nothing here is a diagnosis, an endorsement of any product, or medical advice; treatment decisions should be made with a qualified clinician.
Frequently asked questions
- How well does botulinum toxin work for underarm sweating?
- In a 320-patient placebo-controlled trial, 94% of treated patients had at least a 50% reduction in underarm sweating at 4 weeks, versus 36% on placebo, and mean sweat production fell by about 83%. At 16 weeks, 82% were still responding versus 21% on placebo (Naumann & Lowe 2001).
- How long does one treatment last?
- Typically several months. A meta-analysis of 12 trials reported the underarm effect lasting roughly 3 to 7 months. A palmar systematic review found a mean of about 4.9 to 9.5 months. Duration varies by person, and repeat injections are needed to maintain the result.
- Is it FDA-approved?
- Yes, for severe primary underarm (axillary) hyperhidrosis that topical treatments haven't controlled, at 50 Units per axilla. Use on the palms and soles is common but off-label, meaning outside the specific approved indication.
- Does it work on sweaty palms and feet too?
- Yes, though it is off-label there. A 2026 review of 19 studies found palmar treatment effective with a mean duration of roughly 6 months. The main drawback is that palm and sole injections are more painful and may cause temporary hand-muscle weakness.
- How does it stop sweating?
- It blocks the release of acetylcholine, the nerve signal that switches on sweat glands (chemodenervation). The treated glands are no longer stimulated. The effect is temporary because nerve endings gradually recover.
- What are the main side effects?
- For underarm treatment, label-listed reactions include injection-site pain and bleeding, sweating elsewhere on the body, and flu-like symptoms. All botulinum toxin products carry a boxed warning about rare spread of effect; no definitive serious spread has been reported at the approved underarm dose.
Sources
Primary peer-reviewed studies and official sources first, then reviews and institutional framing (secondary).
- 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. Full text
- Systematic review and meta-analysis. Efficacy and safety of botulinum toxin type A in primary axillary hyperhidrosis: a meta-analysis and systematic review (12 RCTs, 904 patients). PMC12500766. Full text
- Systematic review. Sustained efficacy of botulinum toxin in primary palmar hyperhidrosis: duration, quality of life, and satisfaction (19 studies). Frontiers in Medicine. 2026;13:1795512. Full text
- US Food and Drug Administration / DailyMed. BOTOX (onabotulinumtoxinA) prescribing information: severe primary axillary hyperhidrosis indication and dosing. DailyMed, National Library of Medicine. DailyMed label
How to cite this page
Sweat Explained. Botulinum Toxin for Hyperhidrosis: The Evidence. Published 2026-07-13; last reviewed 2026-07-13. Available at: https://sweatexplained.com/research/botulinum-toxin-for-hyperhidrosis-evidence
Please cite the original studies for the underlying figures. Journalists are welcome to link to this page; the charts are original renderings of the cited data.