How does botulinum toxin act against excessive underarm sweating ?
Botulinum toxin is a purified protein used medically for more than twenty years. It temporarily blocks acetylcholine release at nerve endings. This molecule stimulates sweat glands. Inhibiting the signal interrupts sweat production locally and reversibly.
Contrary to certain misconceptions, this is a functional medical procedure rather than an aesthetic treatment, with effects documented by numerous clinical studies.
Injected superficially into the underarm dermis in a precise grid, botulinum toxin acts only on sweat glands in the targeted area. It affects neither overall body temperature regulation nor other skin functions.
Clinical effectiveness : rapid results
Underarm botulinum toxin effectiveness is extensively proven. Patients notice markedly reduced sweating from the 3rd to 5th day. Maximum effect is generally reached between 7 and 14 days.
Clinical studies show sweating reductions exceeding 80 to 90 % in most treated patients. Benefits extend beyond reduced moisture to its consequences : clothing patches disappear, freshness lasts longer, odour decreases and social and professional comfort improve.
Patients often describe a clear before-and-after transformation : “I spent the whole summer without worrying about my clothes. I did not sweat under my arms once.”
Comparison : underarm botulinum toxin versus other hyperhidrosis treatments
Several options may be considered for primary axillary hyperhidrosis (excessive underarm sweating). However, they differ in effectiveness, comfort and tolerance. Comparing them clarifies the place of botulinum toxin.
Non-prescription aluminium chloride antiperspirants are generally first-line. They temporarily block sweat ducts. They may help mild forms but effectiveness varies greatly. They are also often poorly tolerated, particularly on sensitive skin, causing irritation or even burns.
Iontophoresis is another alternative, mainly for hands and feet. A weak electrical current passes through a water bath to reduce sweat-gland activity. Although effective in some areas, this method is demanding : sessions must be repeated several times weekly and effects disappear quickly when stopped.
Finally, surgery, particularly thoracic sympathectomy, is sometimes considered in extreme cases. It interrupts nerves stimulating sweat glands. Although potentially radical, it carries risks : it is irreversible and may cause complications, particularly excessive sweating elsewhere (compensatory sweating), sometimes difficult to manage.
Which medicine treats excessive sweating ?
Certain anticholinergic medicines may be prescribed for hyperhidrosis, particularly generalised sweating or when topical treatments fail. Medicines such as oxybutynin or glycopyrrolate inhibit acetylcholine, the neurotransmitter stimulating sweat glands. Some patients experience notable benefits, but frequent side effects limit use : dry mouth, constipation, visual disturbances or drowsiness. They are reserved for precise indications and require rigorous medical prescribing. They are not first-line for localised underarm sweating, for which botulinum toxin injections are preferred.
Why is botulinum toxin the reference solution for excessive sweating ?
Botulinum toxin treatment has numerous advantages :
- Rapid effectiveness (from the first week).
- High safety, with a product known and used for over 20 years.
- No social downtime or notable systemic effect.
- Prolonged duration (an average of 4 to 6 months).
- Treatment can be repeated without loss of effect.
In practice, botulinum toxin currently offers the best balance of effectiveness, tolerance and convenience for axillary hyperhidrosis.
Clinical studies on botulinum toxin effectiveness in hyperhidrosis
Several scientific studies have examined botulinum toxin for excessive sweating, particularly in the armpits.
A landmark study published in the Journal of the American Academy of Dermatology showed that :
- 95 % of patients treated with botulinum toxin (100 units, 2 vials divided between both armpits) noticed a sweating reduction exceeding 75 % from the second week.
- Maximum effect occurs on average between the 7th and 14th day, with effectiveness maintained for up to 9 months.
- Quality-of-life scores (DLQI – Dermatology Life Quality Index) improved significantly in more than 90 % of patients.
- No compensatory sweating was observed in these studies.
Does botulinum toxin stop sweating completely ?
Botulinum toxin injections do not eliminate body sweating — which would be harmful — but locally block sweat-gland activity in the treated area. For axillary hyperhidrosis, this means almost no underarm sweating for several months.
In practice, more than 80 % of patients report complete or near-complete absence of underarm sweating for 4 to 6 months. Slight sweating may remain in some patients. This subtle residual effect reflects normal physiological sweat activity but no longer causes discomfort or daily restrictions.
The aim is to regulate sweating where excessive rather than completely block the mechanism. Action is strictly targeted, preserving the body's natural ability to sweat elsewhere when necessary. Overall temperature regulation, essential to physiological balance, remains intact.
Is botulinum toxin a permanent hyperhidrosis treatment ?
Botulinum toxin treatment for hyperhidrosis is not permanent, but reversibility is a major advantage. Effects develop gradually, reach full potential within days and gently fade after an average of six months.
Contrary to common assumptions, patients view this timing as flexibility rather than a constraint : it allows session frequency to follow seasons, treatment to adapt to symptom changes and therapeutic freedom to be preserved.
