Underarm Botox Explained: How It Works for Excessive Sweating

Clinical guidance from Dr Nyla Raja MBChB (Hons), MRCGP (Dist), DFFP, DPDermatology - GMC No. 6057913

What Is Axillary Hyperhidrosis?

Axillary hyperhidrosis means excessive sweating from the underarms.

Sweating is a normal physiological process that helps regulate body temperature. Hyperhidrosis is different: sweating occurs at a level that is disproportionate to the body’s need for cooling and may interfere with clothing, work, social situations, or everyday activities.

Some people experience excessive sweating predominantly in the armpits. Others may also have symptoms affecting the palms, soles, face, or other areas.

The NHS guidance on excessive sweating notes that hyperhidrosis can occur without an obvious cause, but it can also be associated with another medical condition or with medicines.

Primary vs Secondary Hyperhidrosis

Before considering treatment, it is useful to distinguish between primary hyperhidrosis and sweating that is secondary to another cause.

Primary Axillary Hyperhidrosis

Primary hyperhidrosis occurs without another identifiable medical condition causing the excessive sweating.

It often affects relatively specific areas, such as the underarms, palms, or feet, and can begin earlier in life.

The sweat glands themselves are not necessarily larger or more numerous. Instead, the signalling that activates them is excessively active.

Secondary Hyperhidrosis

Secondary hyperhidrosis occurs because of another factor. Possible causes can include medical conditions, hormonal changes, infections, neurological disorders, or medicines.

Sudden onset, widespread sweating, or prominent night sweats should therefore not automatically be treated as a local cosmetic problem.

The current BOTOX clinical prescribing information for axillary hyperhidrosis specifically advises medical history, physical examination, and additional investigation where required to exclude potential causes of secondary hyperhidrosis before treatment.

How Does Underarm Botox Work?

Botulinum toxin type A works by temporarily interrupting communication between nerves and their target tissues.

Underarm sweat is produced predominantly by eccrine sweat glands. These glands are stimulated by nerves that release a chemical messenger called acetylcholine.

When botulinum toxin is injected into the skin of the underarm, it inhibits the release of acetylcholine from the local nerve endings. As a result, the sweat glands within the treated area receive less of the signal that normally tells them to produce sweat.

Sweat production is therefore temporarily reduced.

This is the same broad medicine used in facial botulinum toxin treatment, but the target is different. Cosmetic facial treatment primarily aims to reduce activity in selected muscles, whereas underarm hyperhidrosis treatment targets the nerve signalling responsible for sweat-gland secretion.

Does Underarm Botox Stop You Sweating Completely?

The objective is to substantially reduce excessive underarm sweating, not to prevent the body from sweating altogether.

Treatment is localised to the injected skin. Sweat glands elsewhere in the body continue to function.

It is also unrealistic to promise that every treated patient will experience completely dry underarms at all times. The response varies, and some sweat production can remain.

The clinically relevant outcome is usually whether sweating has reduced enough to improve the problem that led the patient to seek treatment.

Who May Consider Underarm Botox?

Botulinum toxin may be considered for people with significant primary axillary hyperhidrosis, particularly where simpler measures have not provided adequate control.

The licensed BOTOX indication is for severe primary hyperhidrosis of the axillae that does not respond to topical antiperspirants or antihidrotic treatments.

Assessment should consider:

• How frequently the sweating occurs
• Whether it affects one area or the whole body
• How long the problem has been present
• Whether symptoms occur during sleep
• Whether sweating affects clothing or daily activities
• Previous antiperspirants or other treatments
• Current medicines
• Relevant medical history
• Whether another cause of sweating needs investigation

The treatment should not be selected simply because someone occasionally sweats more during hot weather or exercise. Those are normal physiological responses.

What Can Underarm Botox Realistically Improve?

For an appropriately selected patient, treatment can reduce the amount of sweat produced from the treated underarms.

This may help with practical problems associated with axillary hyperhidrosis, including:

• Frequent visible sweat marks on clothing
• The need to change clothes repeatedly
• Difficulty wearing certain fabrics or colours
• Persistent underarm dampness
• Disruption to work or everyday activities

The treatment addresses the sweat production itself. Its purpose is not to change the structure of the underarm or produce a broader cosmetic alteration.

What Underarm Botox Cannot Do

Underarm botulinum toxin is a symptom-control treatment. It should not be described as a cure for every form of excessive sweating.

It does not:

• Permanently switch off the sweat glands
• Treat an underlying thyroid, hormonal, infectious, neurological, or other medical condition causing secondary sweating
• Correct sweating caused by a medicine without addressing the medication itself
• Prevent normal sweating from the rest of the body
• Guarantee completely dry underarms
• Provide a permanent result

If excessive sweating is secondary to another medical problem, managing the underlying condition may be the more important treatment.

What Does Underarm Botox Treatment Involve?

The treatment is different from having a small number of injections into facial muscles.

For primary axillary hyperhidrosis, the hyperhidrotic area may first be identified clinically. In some settings, an iodine-starch test can be used to map where sweating is most active.

The medicine is then injected intradermally at multiple points distributed across the underarm.

The licensed BOTOX protocol recommends 50 units per axilla, distributed evenly across multiple injection sites approximately 1–2 cm apart. Dosing applies specifically to that medicinal product because botulinum toxin units are product-specific and should not be assumed to be interchangeable between different preparations.

The MHRA guidance on botulinum toxin type A products confirms that units cannot be directly interchanged between different botulinum toxin preparations.

When Does Underarm Botox Start Working?

Reduced sweating is not necessarily immediate.

According to the current BOTOX prescribing information, clinical improvement generally occurs within the first week after treatment.

The effect is temporary because the affected nerve endings gradually recover their ability to signal to the sweat glands.

For the licensed BOTOX treatment of primary axillary hyperhidrosis, the effect has been reported to persist for approximately four to seven months, although individual duration varies.

Repeat treatment can be considered when the effect has diminished and further treatment is clinically appropriate. It should be based on individual response rather than assuming everyone needs treatment at an identical interval.

What Are the Side Effects and Risks?

Multiple small injections are required across the underarm, so temporary local effects can occur.

Recognised effects can include:

• Injection-site discomfort
• Minor bleeding or bruising
• Temporary swelling or irritation
• Headache
• Hot flushes
• Changes in sweating elsewhere
• Less commonly, temporary local muscle weakness

The prescribing information reports that increased non-axillary sweating can occur in a minority of treated patients.

As with other botulinum toxin treatments, rare systemic effects are possible. Difficulty swallowing, speaking, or breathing, or significant generalised muscle weakness requires urgent medical assessment.

Our detailed guide to Botox safety explains the wider safety considerations associated with botulinum toxin treatment.

What Other Treatments Are Available for Excessive Sweating?

Botulinum toxin is not necessarily the first treatment used for axillary hyperhidrosis.

Depending on severity and cause, management may include:

• Stronger antiperspirants
• Prescription topical treatments
• Medicines that reduce sweating in selected patients
• Iontophoresis for certain areas
• Botulinum toxin injections
• Selected procedures or surgery in more severe cases

The appropriate sequence depends on where the sweating occurs, its severity, what has already been tried, and whether an underlying cause is present.

The NHS hyperhidrosis guidance provides an overview of self-care, pharmacy options, and specialist treatments.

When Should Excessive Sweating Be Medically Assessed?

Not all excessive sweating should initially be managed as an injectable-treatment concern.

The NHS advises speaking to a GP where excessive sweating:

• Has persisted for at least six months
• Interferes with normal daily activities
• Occurs at least weekly
• Occurs at night
• Is associated with a family history of excessive sweating
• May be related to medicine taken for another condition

Medical assessment is also sensible where sweating has begun suddenly, affects the whole body, or is accompanied by other unexplained symptoms.

These features do not necessarily mean that something serious is present, but they warrant assessment rather than automatically suppressing the symptom with local injections.

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Underarm Botox FAQs

Is underarm Botox the same as cosmetic Botox?

The same type of medicine can be used, but the clinical objective and injection technique are different. Cosmetic treatment usually targets selected facial muscles, whereas treatment for axillary hyperhidrosis uses multiple intradermal injections to reduce signalling to sweat glands.

Does Botox block sweat glands?

It temporarily blocks the nerve signal that activates the sweat glands rather than physically blocking or removing the glands themselves.

Will I still sweat after underarm Botox?

Yes. The aim is to reduce excessive sweating from the treated underarms. Sweat glands elsewhere in the body continue to function, and some underarm sweating may remain.

Is it unhealthy to stop underarm sweating?

Treatment is localised to a relatively small area of the body’s skin. It does not stop the body’s overall ability to sweat and regulate temperature.

How quickly does underarm Botox work?

Clinical improvement with the licensed BOTOX treatment generally develops within the first week. The response can vary between patients.

How long does underarm Botox last?

For primary axillary hyperhidrosis, the effect of BOTOX has been reported to last approximately four to seven months. Individual duration varies, and repeat treatment should be considered according to clinical need.

Does underarm Botox cure hyperhidrosis?

No. It temporarily reduces sweat production in the treated area. The underlying nerve function gradually recovers, which is why the effect wears off.

Can Botox treat sweating caused by another medical condition?

Suppressing local sweating does not treat the underlying disease. Where secondary hyperhidrosis is suspected, the cause should be assessed and managed appropriately.

Can Botox help body odour?

Reducing the amount of underarm sweat may alter the moist environment associated with odour, but botulinum toxin is a treatment for excessive sweating rather than a direct treatment for every cause of body odour.

How many injections are needed in each armpit?

Underarm treatment involves multiple small injections distributed across the sweating area rather than one injection into each armpit. The exact pattern depends on the treatment protocol and area requiring treatment.

What should I do after underarm Botox?

Your practitioner should provide instructions based on the treatment performed. General information on activity, heat, alcohol, rubbing, and other precautions is available in our Botox aftercare guide.

Underarm Botox: Reducing Excessive Sweating Through Local Nerve Signalling

Underarm botulinum toxin can provide temporary control of primary axillary hyperhidrosis by reducing the nerve signals that stimulate sweat production. Its role is therefore different from cosmetic facial treatment even though the underlying medicine may be the same.

Its limitations are equally important. Treatment reduces sweating from the injected area but does not permanently switch off the sweat glands or correct an underlying medical condition responsible for secondary hyperhidrosis.

Appropriate treatment begins by establishing whether the sweating is genuinely excessive, whether simpler treatments have been sufficient, and whether the pattern suggests that further medical assessment is required.

If excessive underarm sweating is affecting your daily life, you can book a free consultation to discuss your symptoms, medical history, suitability, and the appropriate next step. Where sweating is new, generalised, occurs at night, or may reflect another medical problem, assessment by your GP may be more appropriate before considering local treatment.