Excessive Sweating

What Is Botulinum Toxin for Sweating?

Botulinum toxin for excessive sweating means injecting small amounts of botulinum toxin type A into the skin of the area that sweats too much. The aim is to temporarily reduce the stimulation of the sweat glands. Unlike cosmetic use on the face, the target here is not a muscle but the sweat gland. It is a medical use that has been studied for excessive sweating confined to one area and not caused by another illness (primary focal hyperhidrosis).

The popular name for this treatment comes from a product name; the active ingredient is botulinum toxin, and several commercial products contain it. This is how it works: sweat glands are stimulated by sympathetic nerve fibres (part of the nervous system that works involuntarily), which use a chemical messenger called acetylcholine. Botulinum toxin stops these nerve endings from releasing acetylcholine and temporarily cuts off the nerve signal to the gland. The effect is not permanent; it gradually fades over time.

Excessive sweating (hyperhidrosis) is sweating beyond what the body needs. It can be confined to one area (focal) or widespread, and it sometimes affects more than one person in a family. According to a recent guideline, primary hyperhidrosis is sweating that is not caused by a condition affecting the whole body or by an external factor, and it usually occurs in areas with many sweat glands, such as the underarms and hands.

The diagnosis is based on the history of the symptoms and the examination findings. The guideline lists two supporting tests: gravimetric testing (weighing the sweat produced) and the starch–iodine test (Minor's test), which shows the sweating area through a change in colour. For the general features of botulinum toxin, its uses on the face and its general risks, see the Botulinum Toxin page. The dose, dilution and injection points are tailored to each person; the doctor giving the treatment decides on them.

RELATEDBotulinum Toxin

SOURCEPMID 42602382PMID 41572865PMID 29989362

Primary and Secondary Hyperhidrosis

Before botulinum toxin is considered, one question needs answering: is the sweating primary or secondary? Primary hyperhidrosis is a condition in its own right. Secondary hyperhidrosis, by contrast, is the result of an illness or a medicine being taken; in that case, the cause must be investigated first, because suppressing sweating in one area does not remove the cause.

In one study, the records of 415 patients were reviewed: 93.3% had primary and 6.7% had secondary hyperhidrosis. Those with secondary hyperhidrosis were older, and their sweating had more often started after the age of 25. The researchers proposed the following criteria for primary hyperhidrosis: excessive sweating that has lasted for at least six months and has at least four of the features below. These features are:

• It occurs in areas with many sweat glands (underarms, palms, soles, head and face).
• It is on both sides and symmetrical.
• It does not occur during sleep.
• It recurs at least once a week.
• It starts at or before the age of 25.
• There is a family history of similar sweating.
• It limits daily life.

According to a review of the causes of secondary hyperhidrosis, secondary sweating usually starts in a person's thirties or later, while primary sweating starts earlier. Sweating that affects the whole body often suggests a secondary cause; the absence of a family history and the presence of other accompanying symptoms are also clues that point to a secondary cause. Even so, the symptoms overlap, and it is not always easy to tell the two apart.

A study of 420 adults assessed in hospital for recurrent widespread sweating identified more than 130 different causes. The most common diagnoses included solid organ cancers, blood cancers and infections; in 16.7% of patients, no cause was found. Fever, a decline in general health and how long the symptoms had lasted were found to help in deciding whether further investigation was needed. So sweating that continues during sleep, affects the whole body, or comes with fever and a decline in general health is not a question for botulinum toxin; it is first a question of diagnosis, and it is assessed with the relevant doctor.

SOURCEPMID 21334095PMID 39604775PMID 35903938

Why Is Excessive Sweating a Medical Issue?

Excessive sweating is common, and a significant proportion of those affected do not see a doctor about it. Yet scientific sources treat excessive sweating not as a cosmetic preference but as a medical condition that can affect quality of life and for which treatment options exist. This is also why botulinum toxin treatment for sweating is considered a medical use.

According to a recent review, primary hyperhidrosis affects between 2% and 5% of the population. In a study in the United States using a nationally representative sample of 8,160 people, the figure was 4.8%, and 70% of those with excessive sweating reported severe sweating in at least one area. Yet only 51% of those affected had discussed it with a healthcare professional. The main reason for not doing so was the belief that excessive sweating is not a medical condition and that there is no treatment for it.

The psychological burden of excessive sweating has also been studied. In a meta-analysis (an analysis that combines the results of several studies) bringing together a total of 18 studies and 47,053 participants, the prevalence of depressive symptoms in people with primary hyperhidrosis was 18%. However, the results vary markedly depending on the scale used, and comparisons with the general population need to be interpreted with caution.

In practical terms, this means that seeing a doctor about excessive sweating is not an overreaction. This information is not meant for diagnosing yourself; whether your sweating is primary or secondary, which areas it affects and how much it limits your daily life are assessed together at a consultation.

SOURCEPMID 41572865PMID 27744497PMID 42458641

Underarm Sweating

The underarms are the area where the evidence for botulinum toxin in sweating is strongest. Several randomised controlled trials (trials in which participants are randomly assigned to groups) comparing the treatment with a placebo (a dummy treatment with no active ingredient), together with meta-analyses combining these trials, show that the treatment significantly reduces the amount of sweat compared with placebo and lessens the impact of sweating on daily life.

In a meta-analysis combining 12 randomised trials and 904 participants with primary underarm hyperhidrosis, botulinum toxin significantly reduced the measured amount of sweat compared with placebo; compared with other treatments, no statistically significant difference was found. Another meta-analysis combining eight randomised trials (937 participants) in sweating confined to one area also showed improvement over placebo in the amount of sweat, disease severity and quality-of-life measures. However, this analysis rated the overall quality of the evidence as moderate and noted that the data were limited to eight weeks of follow-up.

Individual studies show a similar picture. In a multicentre study in which 320 patients were randomly assigned to groups, 94% of the toxin group and 36% of the placebo group had responded to treatment at week 4; a response was defined as sweat production falling by at least half. At week 16, these figures were 82% and 21%. Another randomised trial included 322 people, with follow-up lasting 52 weeks; a two-point improvement on a four-point disease severity scale was reported in 75% of the toxin groups and 25% of the placebo group.

There are fewer comparative data. A small, open-label randomised trial (in which participants knew which treatment they were receiving) included 25 people. At week 4, the responder rate was 92% in the botulinum toxin group and 33% in the group using aluminium chloride applied to the skin; aluminium chloride was reported to be both effective and well tolerated in 29% of patients. According to a review on the underarms, the injections are given into the skin at several points, and marking the sweating area with the starch–iodine test affects how much of the area the treatment covers and how long it lasts.

SOURCEPMID 40500510PMID 33619611PMID 11557704PMID 17306417PMID 18380203PMID 42602382

Hand Sweating

Botulinum toxin has been found to be effective for sweating of the palms, but the evidence is more limited than for the underarms. Two issues stand out here: injection pain and temporary loss of strength in the hand muscles. When deciding about treatment for sweaty hands, these two issues carry a weight that they do not carry for the underarms.

In one of the early randomised trials in this area, 19 patients had botulinum toxin injected into one hand and a placebo into the other. When measured on day 28, the reduction in sweat was significantly greater in the hand treated with toxin; this small study found no change in grip strength. A recent systematic review (a review that searches for and assesses the studies on a topic using a set method) of 19 studies on primary hyperhidrosis of the palms reported a marked improvement in quality-of-life scores. Patient satisfaction was high but decreased over time; the review stressed the need for standard treatment protocols and for studies that follow patients over a longer period.

Loss of strength was measured in a separate study. In 37 patients who had toxin injected into the skin of the palms, the nerve–muscle responses recorded from the thumb and little-finger muscles were reported to fall markedly at week 3 and to have returned almost to normal at week 37; the reduction in finger strength was more limited. The researchers concluded that the toxin had spread to the underlying muscles despite careful technique and small doses.

According to a systematic review that also assessed areas other than the underarms – the palms as well as sweating of the face and scalp – the effect on the hands is reliable, but the treatment is limited by injection discomfort and temporary weakness. A review on this subject describes the intense pain caused by injections into the palms and soles as the main factor that stops patients from choosing this treatment. Methods to reduce the pain include numbing creams applied to the skin, ice, vibration and nerve blocks (numbing the nerve that carries sensation from the area); each has its own advantages and limitations. Because of injection pain and the possibility of temporary loss of strength, it is important to discuss this at your consultation if your work or hobbies require fine hand skills.

SOURCEPMID 12269876PMID 41958548PMID 11554908PMID 41461243PMID 34743126

Foot Sweating

Botulinum toxin is also used for sweating of the soles, but of the three areas, this is where the evidence is weakest. The data come mainly from reports on individual patients (case reports) and small patient series. Injections into the soles are painful, like those into the palms; pain control is an essential part of the treatment.

According to a review of treatments for sweating of the soles, the scientific data on this subject are clearly insufficient, long-term follow-up data are rare, and larger studies with long follow-up are needed. Promising options include iontophoresis (a treatment using a mild electric current), botulinum toxin and lumbar sympathectomy (surgically cutting the sympathetic nerve chain in the lower back). According to another review, excessive sweating also increases the risk of fungal, bacterial and viral skin infections; this is why everyday measures such as hygiene and the choice of shoes, insoles and socks are also considered.

A relatively large series in this area is based on the retrospective records of 129 patients treated with toxin for sweating of the soles. The average duration of response was 6.16 months. The responder rate, assessed with the starch–iodine test, was reported as 71.67% at one month, 63.44% at three months, 47.78% at six months and 34.13% at nine months. No serious side effects were reported. However, the study is retrospective and has no control group, so the results should be interpreted with caution.

In treating the palms and soles, pain management is seen as a core component that requires skill in several techniques. A small retrospective study of 30 patients treated with toxin for sweating of the palms reported a link between treating the hands and improvement in foot sweating; however, this observation has not been confirmed by a controlled study.

SOURCEPMID 27053510PMID 27215162PMID 37964488PMID 25152344PMID 34743126PMID 34541778

Botulinum Toxin Among the Treatment Steps

Botulinum toxin is neither the first nor the only treatment for excessive sweating. Guidelines plan treatment step by step, according to how severe the sweating is, which area it affects, which treatments have already been tried and what the patient prefers. Where botulinum toxin sits among these steps also depends on these factors.

In the recommendations of the Canadian Hyperhidrosis Advisory Committee, treatment is organised according to a disease severity scale and the area affected. For mild sweating of the underarms, palms and soles, the first step is aluminium chloride applied to the skin. If there is no response, the second step is botulinum toxin, with iontophoresis as an additional option for the palms and soles. For severe sweating, botulinum toxin and aluminium chloride applied to the skin are among the first-step options. Local surgery for the underarms, and endoscopic thoracic sympathectomy (ETS: cutting the sympathetic nerve chain inside the chest using a keyhole method) for the palms and soles, should be considered only after all other options have failed.

A recent guideline lists the following options: medicines applied to the skin, botulinum toxin injections, iontophoresis, radiofrequency, microwave or ultrasound treatments, and surgical procedures (suction curettage, in which the sweat glands in the underarm are removed by suction and scraping, and sympathectomy). Anticholinergic medicines that act on the whole body (systemic), that is, medicines that block the action of acetylcholine, can also be used. A recent review also describes a stepwise approach: first aluminium chloride and anticholinergic medicines, then botulinum toxin. However, there are few high-quality studies on the effectiveness and long-term results of these treatments.

A systematic review comparing microwave treatment, botulinum toxin and suction curettage for the underarms found all three to be effective and safe; the effect of microwave treatment and suction curettage was reported to last longer than that of botulinum toxin, and the review stressed the need for well-designed randomised trials. Sympathectomy, however, has a specific unwanted outcome of its own: compensatory sweating, meaning increased sweating in other parts of the body. In a meta-analysis covering a total of 3,117 patients, the rate of compensatory sweating after surgery was calculated as 62%, and the rate of severe compensatory sweating in four studies as 23%.

SOURCEPMID 17661933PMID 29989362PMID 41572865PMID 27782761PMID 40124609

How Long Does the Effect Last, and Why Is It Repeated?

The effect of botulinum toxin on sweating is temporary: sweating returns over time, and the treatment must be repeated to maintain the effect. How long it lasts depends on the area, the product and dose used, the severity of the sweating and the individual. So the durations reported in studies do not show how long the effect will last for you.

According to a review on the underarms, the effect of each treatment typically lasts about four to seven months. In the systematic review of 19 studies on primary hyperhidrosis of the palms, the effect lasted between three and twelve months; higher doses and repeated injections were associated with longer symptom control, and moderate sweating with longer relief than severe sweating. In the series of 129 patients treated on the soles, the responder rate was reported to fall gradually over the months.

According to a review on treating the palms and soles, patients are highly satisfied with this treatment and usually come back for a repeat treatment every six months. On the other hand, in the meta-analysis combining eight randomised trials in sweating confined to one area, long-term results could not be assessed because the data were limited to eight weeks of follow-up. In short, there are few controlled data on how repeated treatments perform in the long term, and these durations cannot replace an expectation based on your own situation.

Another question that comes up with repeated treatments is whether the body develops antibodies that make the toxin ineffective (neutralising antibodies). In an umbrella review that brought together five systematic reviews (203 studies, 17,815 patients), the rate of neutralising antibodies in excessive sweating and cosmetic uses was found to be almost negligible. However, the methodological quality of the reviews included in this umbrella review was rated as ranging from low to critically low.

SOURCEPMID 42602382PMID 41958548PMID 37964488PMID 25152344PMID 33619611PMID 35139064

Limits of This Treatment

Botulinum toxin is a treatment that reduces sweating temporarily; it does not cure excessive sweating or remove its cause, and the sweating returns when the effect wears off. Its benefit is meaningful when it is used to answer the right question, that is, primary sweating confined to one area.

In secondary hyperhidrosis, the limit is clearer. According to a review of the causes of secondary hyperhidrosis, sweating that affects the whole body often suggests a secondary cause, and in that case the underlying cause needs to be assessed and addressed. Suppressing sweating in one area does not affect the underlying condition.

The evidence differs from area to area. For the underarms, the evidence is based on randomised trials. On the palms, the effect has been found to be reliable, but the treatment is limited by injection discomfort and temporary weakness. For the soles, the scientific data are clearly insufficient and long-term follow-up data are rare. For sweating of the face and scalp, the data come mainly from small groups of patients and case series.

The limits of the evidence are also clear in the overall picture. According to a recent review, there are only a few high-quality studies on the effectiveness and long-term results of treatments for excessive sweating. A meta-analysis combining randomised trials in sweating confined to one area also found the overall quality of the evidence to be moderate, and stressed the need for studies comparing botulinum toxin with first-step treatments. At which step botulinum toxin makes sense for you is discussed at your consultation, based on how severe your sweating is and where it occurs.

SOURCEPMID 41572865PMID 33619611PMID 27053510PMID 41461243PMID 39604775

Known Risks

Botulinum toxin treatment for sweating is a medical procedure using a prescription-only medicine, and it has side effects. Most of the adverse effects reported in studies are mild, local and temporary, but the main risk differs by area. The findings here come from studies in other people and cannot be used to calculate your personal risk.

Underarms: According to a review, adverse effects are mostly mild and limited to the injection site. The meta-analysis combining 12 randomised trials in primary underarm hyperhidrosis also found botulinum toxin to be associated with fewer side effects than the other treatments it was compared with. In this area, the injections are given into the skin; the target is the sweat glands, not the muscles underneath.

Palms: There are two main issues. The first is temporary loss of strength in the hand muscles. A study of 37 patients treated on the palms reported that the toxin spread to the underlying muscles despite careful technique and small doses, and that nerve–muscle responses fell markedly at week 3 and had returned almost to normal at week 37. A small randomised trial, however, found no change in grip strength. The second issue is injection pain; one review describes this pain as the main factor that stops patients from choosing this treatment.

Soles: No serious side effects were reported in the retrospective series of 129 patients. However, a retrospective study with no control group can give only limited information about rare adverse effects. Injections into the soles are painful, like those into the palms.

Situations that need particular care: A systematic review of the link between myasthenia gravis (a neuromuscular disorder) and botulinum toxin reported that marked muscle weakness developed in all eight people with not-yet-diagnosed myasthenia who were given the toxin. According to a review of cosmetic treatments during pregnancy and breastfeeding, the safety data on botulinum toxin are insufficient, and better evidence is needed before firm recommendations can be made.

For this reason, you should tell the doctor at your consultation if you have a known neuromuscular disorder, if you could be pregnant or if you are breastfeeding. Which symptoms after the treatment mean you should contact the clinic is explained at your consultation, according to the doctor's own protocol.

SOURCEPMID 42602382PMID 40500510PMID 11554908PMID 12269876PMID 34743126PMID 37964488PMID 34929650PMID 28492048