Sweating is an essential physiological phenomenon, but when it becomes excessive, localized, and uncontrollable, it is called hyperhidrosis. It mainly affects certain areas rich in sweat glands, such as the underarms, hands, feet, or face. Among these locations, axillary hyperhidrosis is one of the most frequent and also one of the most troublesome.
It can occur without any physical effort, without exposure to heat, and even at complete rest. Patients affected suffer from constant sweating, which causes visible sweat stains, a permanent feeling of moisture, clothing discomfort, and often significant social embarrassment. When local solutions (antiperspirants, technical clothing) prove ineffective, it is legitimate to consider a targeted medical treatment.
In this context, botulinum toxin injections — better known as Botox — have become the reference treatment for axillary hyperhidrosis.
Botulinum toxin is a purified protein, used in medicine for over twenty years. It works by temporarily blocking the release of acetylcholine at the nerve endings. This molecule is responsible for stimulating the sweat glands. By inhibiting this signal, Botox interrupts sweat production in a localized and reversible way.
Contrary to some common misconceptions, this is not a cosmetic treatment, but a functional medical procedure, whose effects are documented by numerous clinical studies.
Injected into the dermis of the underarms, at shallow depth and following a precise grid pattern, Botox acts only on the sweat glands of the targeted area. It does not affect the body’s overall thermoregulation or other skin functions.
The efficacy of axillary Botox is now well established. From the 3rd to the 5th day after injection, patients notice a marked reduction in sweating. The maximal effect is generally reached between 7 and 14 days.
Clinical studies show a reduction in sweating of more than 80 to 90 % in the vast majority of treated patients. This efficacy is not limited to the decrease in moisture itself, but also extends to its consequences : disappearance of underarm stains on clothing, prolonged sensation of freshness, reduction of body odors, improvement of social and professional comfort.
Patients often describe this transformation as a very clear “before/after” : “I went through the whole summer without worrying about my clothes. I didn’t sweat once under my arms.”
When a person suffers from axillary hyperhidrosis (excessive underarm sweating), several therapeutic options can be considered. However, not all offer the same level of efficacy, comfort, and tolerability. Comparing them helps to better understand the role of botulinum toxin treatment.
Aluminum chloride–based antiperspirants, available without prescription, are generally proposed as first-line therapy. Their action relies on temporarily blocking the sweat gland ducts. They can be useful in mild cases, but their efficacy remains very inconsistent. Moreover, they are often poorly tolerated, particularly on sensitive skin, where they may cause irritation or even burns.
Iontophoresis is another alternative, mainly used for hands and feet. It consists of passing a low-intensity electric current through a water bath in order to reduce the activity of the sweat glands. While it may provide good results for certain areas, this method remains restrictive : sessions must be repeated several times per week, and the effects disappear quickly once treatment is stopped.
Finally, surgery, particularly thoracic sympathectomy, is sometimes considered in extreme cases. It involves interrupting the nerves responsible for stimulating the sweat glands. While it may provide a radical solution, it is not without risks : it is an irreversible procedure that can lead to complications, especially excessive sweating in other areas of the body (compensatory sweating), which can sometimes be difficult to manage.
In the treatment of hyperhidrosis, certain anticholinergic medications may be prescribed, particularly in cases of generalized sweating or when local treatments prove ineffective. These molecules, such as oxybutynin or glycopyrrolate, act by inhibiting the action of acetylcholine, the neurotransmitter responsible for stimulating the sweat glands. Their efficacy can be significant in some patients, but their use remains limited due to frequent side effects : dry mouth, constipation, visual disturbances, and even drowsiness. These treatments are therefore reserved for specific indications and must be prescribed under strict medical supervision. They are not considered a first-line solution for localized sweating, such as under the arms, where botulinum toxin injections are the treatment of choice.
Botulinum toxin treatment has many advantages :
In practice, Botox now represents the best compromise between efficacy, tolerability, and ease of use for axillary hyperhidrosis.
Several scientific studies have investigated the effect of botulinum toxin in the treatment of excessive sweating, particularly in the underarms.
A landmark study published in the Journal of the American Academy of Dermatology showed that :
The injection of botulinum toxin does not suppress sweating throughout the body — which would be harmful — but it locally blocks the activity of the sweat glands in the treated area. In the case of axillary hyperhidrosis, this means an almost complete disappearance of underarm sweating for several months.
In practice, more than 80 % of patients report a total or near-total absence of underarm sweating for 4 to 6 months. In some patients, slight sweating may persist after treatment. This is a residual, subtle phenomenon corresponding to normal, physiological sweat activity. But this sweating no longer causes discomfort or constraints in daily life.
What is important to understand is that the treatment does not aim to completely block the sweating mechanism, but to regulate it where it becomes excessive. Its action is strictly targeted, thus preserving the body’s natural ability to sweat elsewhere when necessary. The overall thermoregulatory function, essential for the body’s balance, therefore remains perfectly intact.
The treatment of hyperhidrosis with botulinum toxin is not permanent, but it is precisely this reversible nature that makes it one of its major advantages. Its effect develops gradually, reaches its full potential in a few days, and then fades gently after an average of six months.
Contrary to common belief, this timing is not perceived as a constraint by patients, but as a form of flexibility: it allows the treatment schedule to be adapted according to the seasons, to modulate the treatment based on symptom evolution, and to preserve therapeutic freedom.
Article written by Dr Romano Valeria
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