Excessive underarm sweating is a real medical complaint. On this page you will read what causes it and which options are available.
The complaint
De klacht
Do you notice wet patches on your shirt before you have even left the house, regardless of the weather or how calm you feel? Excessive underarm sweating, medically known as axillary hyperhidrosis, is more than just sweating a lot. The sweat glands under your arms are overactive and keep producing without any need for heat or exertion. That is unpleasant, but it is a known and treatable condition, not a matter of hygiene or willpower.
Mogelijke aanpak
One possible approach for axillary hyperhidrosis is injections with botulinum toxin into the skin of the underarm. The product temporarily blocks the nerve signals to the sweat glands, reducing sweat production in the treated area. Whether this is suitable for you depends on your situation and is first assessed during a consultation.
I only treat underarm sweating after we have checked together whether there is no underlying cause and whether simpler steps such as a stronger antiperspirant have already been tried. Botulinum toxin is a temporary, local treatment, not a permanent solution.
Sweating is normal and healthy: it is your body's way of regulating its temperature. With axillary hyperhidrosis, however, sweat production in the armpits is disconnected from that need. You sweat even in a cool room, at rest, or under mild stress, often so profusely that clothing becomes visibly wet. Many people adjust their behavior because of it: choosing dark or loose clothing, wearing double t-shirts, keeping their arms close to their body, or avoiding situations where they feel vulnerable.
We speak of primary hyperhidrosis when the excessive sweating stands on its own, usually starts at a young age, occurs symmetrically on both sides, and typically disappears during sleep. In secondary hyperhidrosis, there is an underlying cause, such as a thyroid problem, hormonal changes, certain medications, or night sweats. That distinction matters, because the right approach differs.
In primary axillary hyperhidrosis, the cause lies in overactive nerve signals to the sweat glands, without anything being wrong with the glands themselves. There is often a familial predisposition. The condition is therefore not the result of poor hygiene or nervousness, even though stress can intensify the sweating.
A consultation is advisable if the sweating interferes with your daily life, your work, or your social contacts, if simple antiperspirants are not enough, or if the sweating started suddenly, occurs on one side only, happens at night, or is accompanied by weight loss, fever, or palpitations. In that last case, we first look for a possible underlying cause before considering a local treatment. Being honest about limits is part of that: sometimes a referral to your GP or another specialist is the right step.
There is no single solution that works for everyone. The choice depends on the severity, what you have already tried, and your overall health. Usually, we work from simple to more invasive.
If the first steps do not produce enough results, botulinum toxin can be an option. The product is injected into the skin of the armpit through small, superficial injections (intradermal). There it temporarily blocks the nerve impulses that drive the sweat glands, so that sweat production in the treated area usually decreases noticeably. It is a targeted, local treatment: glands elsewhere in the body keep working normally, so your body can continue to regulate its heat as usual.
Your nerve endings normally release a messenger substance that tells the sweat gland to sweat. Botulinum toxin temporarily interrupts that signal. The effect is therefore reversible: as the nerve endings recover, sweat production gradually returns. That is why a repeat treatment is needed to maintain the result. The effect is usually noticeable within 3 to 7 days and typically lasts several months, often in the range of 4 to 9 months, although this varies greatly from person to person.
The treatment can be useful when excessive underarm sweating bothers you and simpler measures fall short, and when an underlying cause has been ruled out. Botulinum toxin is generally not recommended during pregnancy or breastfeeding, with certain neuromuscular disorders, with an infection or skin problem in the armpit area, or with a known hypersensitivity to the product. If a secondary cause is at play, we focus on that first. During the consultation, I review your medical history and medication to determine whether it is a responsible choice for you.
Everything starts with a consultation. We discuss your complaint, how long it has been going on, what you have already tried, and whether there are signs that point to an underlying cause. That way we decide together whether a treatment is appropriate and, if so, which one. If you choose botulinum toxin, the areas that sweat the most are marked, after which the small injections are distributed across the armpit skin. The session itself usually takes 15 to 30 minutes. The pricks are superficial; a numbing cream is optional. You can usually resume your day afterwards. Intense exercise, sauna, and heat are best avoided for the first few hours. What a treatment costs is discussed during the consultation, tailored to your situation.
Side effects are usually mild and temporary: slight tenderness, redness, or a bruise at the injection sites. Sometimes the body shifts its heat regulation to other areas, so you may temporarily sweat a bit more elsewhere. Rarer effects and how we monitor them are discussed beforehand. Be aware of the limit: this is a temporary treatment that can reduce sweating in the treated area, not a cure and not a guarantee that you will never sweat again. How your body responds varies from person to person.
Botulinum toxin is not the only path and certainly not always the first. For many people, a stronger antiperspirant, iontophoresis, or, in consultation, medication is an appropriate solution. In stubborn cases, there are further medical options that require a specialized assessment. Which route makes the most sense depends on your complaint and expectations; we weigh that together during the consultation.
Dr. T explains
For underarm sweating, I don't inject into a muscle but very superficially into the skin, exactly where the sweat glands are located. Botulinum toxin temporarily interrupts the nerve signal that triggers the gland to sweat. Because the body gradually repairs those nerve endings, the effect is temporary and sweating returns over time. Elsewhere in your body, sweat regulation continues to work normally, so your heat balance remains intact.
Dr. Thierry De Smedtaesthetic physician, Ghent
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