Botulinum toxin A for primary axillary hyperhidrosis: a narrative review.

Primary axillary hyperhidrosis (PAH) markedly impairs psychosocial well-being and daily functioning. Botulinum toxin type A (BoNT-A) is widely used, both on- and off-label, to suppress eccrine sweating through presynaptic inhibition of acetylcholine release and temporary chemodenervation of cholinergic sympathetic fibers. This narrative review synthesizes published clinical evidence between 2000 and January 2025 regarding the efficacy, durability, safety, and quality-of-life outcomes of BoNT-A for PAH, with comparative consideration of toxin formulations, injection techniques, and device-based alternatives. Evidence from randomized trials, prospective cohorts, long-term observational studies, and meta-analyses consistently demonstrates that intradermal BoNT-A achieves substantial axillary sweat reduction, often exceeding 50-80%, with improvement of at least two grades on the Hyperhidrosis Disease Severity Scale and meaningful reductions in Dermatology Life Quality Index scores. Treatment effects typically persist for approximately 4-7 months per cycle and are associated with predominantly mild, localized adverse events. Comparative data indicate similar efficacy among onabotulinumtoxinA, incobotulinumtoxinA, and abobotulinumtoxinA when equivalent dosing and standardized mapping techniques are applied. Injection strategy, particularly multi-point intradermal delivery guided by starch-iodine mapping, influences coverage and durability. Energy-based modalities-including microwave thermolysis and fractional microneedle radiofrequency-reduce sweating via device-mediated thermal targeting of eccrine glands and show variable comparative outcomes versus intradermal BoNT-A in durability, downtime, and cost. Overall, BoNT-A remains a well-supported first-line injectable therapy for PAH refractory to topical treatment, while further head-to-head and cost-effectiveness studies remain warranted.