Excessive Sweating (Hyperhidrosis): Causes and Underarm Treatment

You change your shirt during the day, the marks under your arms soak through the fabric and, in meetings, you keep your elbows pressed to your sides. Excessive underarm sweating weighs on work and relationships alike. When you sweat more than the heat or exertion explains, it is called axillary hyperhidrosis. Before thinking about a treatment, the doctor first finds out what is making you sweat this much.

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Fictional man wearing a light-coloured shirt, standing in a bright streetcar, holding a grab bar with his arm slightly raised, looking a little self-conscious, with no visible trace of sweat.

At a glance

Five things to know before deciding

What axillary hyperhidrosis is: heavy sweating under the arms, even in cool conditions or at rest, that gets in the way of daily life; in its most common form, no other condition is the cause.
When to look for a cause first: sweating during sleep, a medication or condition behind it, or unexplained sweating with fever, weight loss, chest pain, shortness of breath or a fast heartbeat; the doctor then looks for the cause before any injection.
What the injection does: it blocks the nerve signal that tells the gland to work, and sweating decreases temporarily in the injected area; it does not treat the cause and does not stop all sweating.
Duration: several months, varying from person to person, with no guarantee; the injection is repeated when the effect fades.
Risk and assessment: mostly pain at the injection site, sometimes a bruise; a medical assessment comes before any treatment.

Hyperhidrosis or Normal Sweat: How to Tell the Difference

Normal sweating cools the body: it shows up in hot weather, during exercise, whenever you might be too warm. In hyperhidrosis, you sweat even though the body does not need to cool down, in cool weather or sitting at a temperature most people find comfortable. Seeing sweat during intense exercise or in great heat therefore does not mean you have it.

Fictional woman, fully clothed, sitting at a meeting table in a bright office, arms held close to her body in a reserved posture, with no visible sweat.

It often starts in childhood or adolescence, and most people affected are otherwise healthy. It can still weigh heavily: some adults avoid meeting people, at work and in their social lives. Only a doctor can confirm that it is hyperhidrosis.

Normal sweating: Triggered by heat or exertion and proportionate, it cools the body.
Hyperhidrosis: Heavy sweating even in cool conditions or at rest, which gets in the way of daily life (clothing, relationships, work).
Primary, or focal, hyperhidrosis: Limited to one or two areas, such as the underarms, in a person who is otherwise healthy.

What Causes Underarm Hyperhidrosis

In the most common form, primary hyperhidrosis, no disease is involved. It affects one or two areas of the body, such as the underarms, palms, soles of the feet or head. It is thought to come from faulty signals from certain nerves, the ones that tell the body when to sweat. If someone in your immediate family sweats a lot, or if your sweating stops during sleep, this may point to this form of hyperhidrosis.

The secondary form comes from something else: a medication you take or another condition. Known causes include certain antibiotics, antivirals, insulins and antidepressants, diabetes, Parkinson's disease, rheumatoid arthritis, heart failure, a stroke, menopause, or withdrawal from alcohol or drugs. Unlike the primary form, it can also cause sweating during sleep.

When to Look for a Medical Cause Before Any Treatment

Before an injection, the doctor checks whether a medication or a disease, such as an overactive thyroid, is making you sweat. Reducing the sweat would not be enough: the disease causing it also has to be recognized and treated. The injection is postponed while the doctor investigates the cause.

If you recognize yourself in any of these situations, talk to a doctor about your sweating. They may order tests to look for another disease. Keep taking any prescribed medication until you have talked with the doctor who prescribed it. If the sweating comes with fever, weight loss, chest pain, shortness of breath or a fast, pounding heartbeat, see a doctor to find the cause: an injection is not the answer to these signs.

What an Injection That Reduces Sweat Gland Activity Does—and What It Does Not Do

This is not a wrinkle being treated here; it is a gland. A sweat gland produces sweat when a nerve sends it a chemical signal. The injection blocks that signal where it is given: the gland then produces less sweat for several months. The injection that reduces sweat gland activity is the same type of injection as the muscle-relaxing injection. The target is not the same, however: the frown line injection and the masseter injection act on a muscle, whereas under the arms the treatment acts on a gland. Assessment and risks therefore depend on the area. It is also called a neuromodulator, with well-known brand names such as Botox^® or Dysport^®; for underarm sweating, the doctor specifies the product at the assessment.

There is no single best treatment for everyone. The treatment of excessive underarm sweating is chosen with the doctor; the injection is one of the options.

Acts on: The nerve signal that tells the gland to work, and so the sweat produced in the injected area, not the cause of the hyperhidrosis.
Who it is for: An adult whose underarm sweating gets in the way of daily life. If antiperspirants are not enough or irritate the skin too much, the doctor may consider the injection with you at the assessment.
What it does not guarantee: Neither the end of all sweating, nor the extent or duration of the result, which vary from person to person.
Who gives it: A doctor, or a nurse injector supervised by a doctor.
Areas and product: For the underarms, the doctor specifies the product and its limits at the assessment. If you also sweat from your hands, feet or face, ask whether that area can be treated before you decide.

When the injection is postponed

If a medical cause is still being looked for.

The injection is not given on inflamed or infected skin, or in cases of hypersensitivity to an ingredient in the product.

How Long the Effect Lasts

The effect is not immediate: sweating decreases in the days after the injection. The effect is temporary: sweating gradually returns after several months. The result and its duration vary from person to person. When the effect fades, the injection is repeated; the timing is discussed at the assessment, depending on your sweating and what you expect.

Risks of an Underarm Injection and Signs That Require Medical Attention

Pain at the injection site is very common. Talk with the doctor about discomfort during the injection. A bruise, bleeding, swelling, irritation or itching are also possible at the same spot, as after any injection. You may also have headaches, tingling, hot flashes, nausea, weakness or muscle pain at the injected area, or notice an unusual skin odour. Fear of the needle or the pain can cause a brief spell of faintness, with a drop in blood pressure and sometimes fainting. Sweating can also increase somewhere other than under the arms: this affects a minority of people, in the month after the injection. An allergic reaction is possible. Rarely, the product spreads far from the injection site; this is a serious effect.

Call CARE MD if you are worried about significant swelling, redness or pain, signs of infection at the injection site, unusual weakness or an unusual effect that persists. Only a doctor can tell what it is.

At the injection site: Pain, bruising, bleeding, swelling, irritation, itching.
Elsewhere in the body: Headache, tingling, hot flashes, nausea, local muscle weakness or pain.
Sweating elsewhere: Possible in the month that follows, in a minority of people.
Allergic reaction: Possible; report it right away.
Rare but serious: The product spreading far from the injection site.

Seek care right away

If you have trouble swallowing, speaking or breathing after an injection. These signs call for immediate medical care.

Other Options: Antiperspirants and Other Treatments

Treatment of hyperhidrosis often starts with products applied to the skin. An antiperspirant temporarily blocks the sweat glands and reduces visible sweat. Those from the pharmacy, sold over the counter, are enough only for mild hyperhidrosis; many people need a prescription antiperspirant. Products based on aluminum salts, such as aluminum chloride, are the first choice for the underarms. They are applied to dry skin, before bed. They sometimes irritate the skin or discolour it under the arms: if this happens to you, tell the doctor. If the product irritates the skin too much or does not reduce the sweat enough, the doctor may consider the injection with you. The pharmacist can also suggest antiperspirants stronger than a deodorant and underarm shields that protect clothing.

If you still sweat too much, a doctor may suggest other treatments: a cloth soaked in a prescription medication to apply under the arms, pills that reduce sweating, iontophoresis (a weak electric current passed through water or a damp pad), microwave thermolysis in a clinic, or surgery that removes the sweat glands. The doctor or pharmacist will tell you which are available in Canada.

Natural remedies, for their part, are about comfort: wear loose clothing, avoid synthetic fabrics such as nylon and tight clothing, and limit what makes sweating worse, such as alcohol or spicy foods. These measures help without treating the cause.

Antiperspirants: Aluminum salts applied to dry skin before bed; over the counter for a mild form, by prescription for the others; they can irritate the skin.
Other medical treatments: Medication applied to the skin or pills, iontophoresis, thermolysis, surgery on the sweat glands.
Simple measures: Loose clothing, non-synthetic fabrics, less alcohol and fewer spicy foods.
Offered by CARE MD: The injection; if another treatment suits you better, the doctor will refer you.

Why a Medical Assessment Comes First

Before suggesting any treatment, the doctor needs to know your history. They ask which medications you take, with or without a prescription. They also want to know how long and how often you have been sweating, where on your body, whether anyone in your family also sweats a lot and what the sweating changes in your life. A physical exam or tests may be needed to find a cause.

The assessment may also lead to postponing or changing the injection, or to the doctor deciding not to perform it. Pregnancy, inflamed or infected skin, or hypersensitivity to an ingredient in the product may lead the doctor to make this decision.

Prepare details of your medical history and a list of your allergies, medications, supplements and treatments already tried, including antiperspirants: they can change the plan. Also mention whether you are pregnant or breastfeeding. Aspirin, certain anti-inflammatories and vitamin E promote bruising: mention them, without stopping them on your own, and the doctor will tell you what to do. Also prepare your questions about what you can expect, the risks, the duration and what happens if the effect does not suit you.

Ask Us Your Questions About Excessive Underarm Sweating

Frequently Asked Questions

How can you tell excessive underarm sweating from normal sweat?

Normal sweating cools the body: it shows up in heat or during exertion. In hyperhidrosis, you sweat even though the body does not need to cool down, for example in cool weather or sitting at a comfortable temperature, and it gets in the way of your daily life. Only a doctor can confirm the diagnosis.

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