Botox Units for Underarms: 25 vs 50 vs 100 — What the Studies Show
The licensed Botox® dose for primary axillary hyperhidrosis is 50 units per underarm — 100 units total. This figure comes from Naumann & Lowe's 2001 BMJ randomised trial and remains the MHRA- and FDA-approved standard. 25 units per side under-treats most patients; 100 units per side is reserved for severe cases. This guide walks through what each dose actually achieves — citing the studies that established the evidence.
Three doses, three durations — but only one is the licensed standard
Quick Answer (PubMed-grounded)
- 25 units / axilla: Sub-therapeutic. ~50% sweat reduction, lasts 2–3 months. Rarely recommended.
- 50 units / axilla: Licensed standard (Naumann BMJ 2001). 80–95% reduction, lasts 6–7 months.
- 75 units / axilla: Modest extension of duration over 50U (Lowe JAAD 2007). Marginal benefit.
- 100 units / axilla: Off-label, severe cases. Lasts up to 9–12 months. Higher cost, similar peak effect.
What the Studies Actually Say
Botox for axillary hyperhidrosis is one of the most rigorously studied applications of botulinum toxin type A in dermatology. The dose was not chosen by clinicians on a hunch — it emerged from a sequence of randomised placebo-controlled trials in the late 1990s and early 2000s that have since been replicated repeatedly.
The pivotal trial is Naumann & Lowe (BMJ 2001): 320 patients with primary axillary hyperhidrosis randomised to 50 units of onabotulinumtoxinA per axilla or placebo. At week 4, 94% of treated patients achieved a ≥50% reduction in spontaneous axillary sweat production, compared with 36% on placebo. Median duration of response was approximately 7 months. This study established the licensed dose still used today.
Lowe et al. (JAAD 2007) followed with a 52-week multicentre double-blind RCT comparing 50 vs 75 units per axilla against placebo. Both active doses were significantly more effective than placebo. The 75-unit arm extended median duration only modestly — confirming that 50 units sits at the rational ceiling of the dose-response curve for most patients.
Heckmann et al. (NEJM 2001) studied abobotulinumtoxinA (Dysport) using 200 units per axilla — biologically equivalent to roughly 50–67 units of Botox® depending on the conversion ratio applied. Effect was robust and sustained. This trial confirmed the class effect across botulinum toxin formulations.
25 Units Per Underarm — The Under-Dose Trap
Some clinics advertise underarm Botox at 50 units total — 25 per side — to hit a low headline price. This is half the licensed dose and sits below the clinically validated therapeutic threshold. Patients typically experience a partial response: sweating is reduced but not abolished, and the effect wears off within 8–12 weeks rather than the 24–28 weeks reported in peer-reviewed trials at the standard dose.
The economics are deceiving. Under-dosed treatment costs less per session but needs to be repeated three to four times a year instead of once or twice — costing more annually for a less complete result. We do not recommend 25 units per side as a first-line treatment.
50 Units Per Underarm — The Evidence-Based Standard
This is the dose your dermatologist or aesthetic doctor should be quoting. 50 units of onabotulinumtoxinA is the dose used in Naumann's pivotal trial, the dose approved by the MHRA and FDA, and the dose at which the published efficacy figures (94% response rate, 6–7 month median duration) apply. The product is delivered as 10–15 small intradermal injections per axilla, mapped using a starch-iodine test or simply by the borders of hair-bearing skin.
At CosmeDocs, axillary hyperhidrosis treatment defaults to 50 units per side unless there is a specific clinical reason to escalate. The treatment takes around 20 minutes, requires only topical anaesthesia or ice, and patients typically return to normal activity the same day.
100 Units Per Underarm — When More Is Justified
100 units per axilla — 200 units total — is an off-label higher dose used in three specific situations: patients with severe hyperhidrosis (Hyperhidrosis Disease Severity Scale grade 4) who have had incomplete response to the standard dose, patients prioritising maximum duration over cost, and a small subset where the sweat-producing area extends beyond the typical hair-bearing axilla.
The trade-off is honest: roughly double the cost for a marginal extension of duration (typically 9–12 months instead of 6–7) and no meaningful improvement in peak efficacy. For most patients with moderate hyperhidrosis, this is not the right starting dose.
Dose Comparison — At a Glance
| Dose / axilla | Sweat reduction | Duration | Status |
|---|---|---|---|
| 25 units | ~50%, partial | 2–3 months | Sub-therapeutic |
| 50 units | 80–95% | 6–7 months | Licensed standard |
| 75 units | 85–95% | 7–8 months | Mild extension (Lowe 2007) |
| 100 units | 85–95% | 9–12 months | Off-label, severe cases |
Why Dose Is Only Half the Story
Two patients receiving 50 units per axilla can have meaningfully different outcomes — because dose is only one of three variables that determine result. The second is distribution: 50 units delivered as 10 evenly spaced intradermal injections covers more sweat-gland territory than the same 50 units delivered as 5 deeper injections. The third is mapping: the sweating area in some patients extends beyond the visible hair-bearing axilla, and a starch-iodine test (Minor's test) reveals this before injection.
At CosmeDocs we map the active sweating zone before treatment, then distribute the dose uniformly across it. This is why two clinics quoting "50 units per side" can produce different durations and patient satisfaction — technique compounds dose.
The "£199 underarm Botox" warning
Treatment priced significantly below the cost of 100 units of branded Botox® plus medical time is, mathematically, either using less product than advertised or using an unbranded toxin without the trial evidence above. Always ask: what brand, what dose per side, and how is the area mapped? Reputable clinics answer all three without hesitation.
References (PubMed)
- 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. PMID: 11557704.
- Lowe NJ, Glaser DA, Eadie N, Daggett S, Kowalski JW, Lai PY; North American Botox in Primary Axillary Hyperhidrosis Clinical Study Group. 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. PMID: 17207833.
- Heckmann M, Ceballos-Baumann AO, Plewig G; Hyperhidrosis Study Group. Botulinum toxin A for axillary hyperhidrosis (excessive sweating). N Engl J Med 2001;344(7):488–493. PMID: 11172190.
- Naumann M, Lowe NJ, Kumar CR, Hamm H. Botulinum toxin type A is a safe and effective treatment for axillary hyperhidrosis over 16 months. Arch Dermatol 2003;139(6):731–736. PMID: 12810504.
- Doft MA, Kasten JL, Ascherman JA. Treatment of axillary hyperhidrosis with botulinum toxin: a single surgeon's experience with 53 consecutive patients. Aesthetic Plast Surg 2011;35(6):1079–1086. PMID: 21626294.