What Causes Excessive Sweating (Hyperhidrosis)?

The human body has about four million sweat glands.

Many of these glands release fluid (a process called sweating) on the surface of a person’s skin when they’re hot, a normal bodily process that helps regulate a person’s body temperature.

Sweating moistens the skin and evaporative cooling helps cool the body down.

Sweat glands are controlled by the nervous system. Excessive sweating (or hyperhidrosis) usually results from an over activation of the sympathetic nervous system (SNS).

The SNS is activated during times of stress and is often associated with the “fight or flight” response to stress.

During times of stress, the SNS causes multiple changes in the body  including, increased respiratory rate, vasodilation (dilation of blood vessels), vasoconstriction (narrowing of blood vessels), and perspiration (sweating).

In this article, I’ll go over what hyperhidrosis is and what may cause it.

I’ll also cover how it’s diagnosed, possible treatments, and when to see a healthcare provider. 

What is Excessive Sweating (Hyperhidrosis)?

Hyperhidrosis is a medical condition that causes a person to sweat excessively.

Any sweating beyond what is necessary for temperature regulation is considered excessive.

When a person has hyperhidrosis, the sympathetic nervous system releases excessive amounts of acetylcholine which activates sweat glands.

There are a few possible causes for this, including some medications and medical conditions. Hyperhidrosis is classified into two types, primary and secondary.

Primary Hyperhidrosis

Of the two types of hyperhidrosis, primary hyperhidrosis usually starts earlier in life due to unknown causes, and symptoms tend to be more limited.

Primary hyperhidrosis is triggered when sweat glands are activated by nerves that haven’t been signaled by physical activity or a rise in temperature.

Sometimes this can happen when you’re feeling anxious or under pressure.

Symptoms of primary hyperhidrosis include: 

• Excessive sweating for six months or more
• Sweating involving armpits, the palms of the hands, soles of the feet and/or face
• Sweating occurring on one side of the body
• Little to no sweating at night
• Sweating episodes that last at least a week
• Experiencing the symptoms at 25 years old or younger
• A family history of excessive sweating
• Sweating impairing the activities of daily life 

Secondary Hyperhidrosis

Secondary hyperhidrosis usually affects the whole body and typically presents due to adverse effects of certain metabolic disorders, anxiety, cancer, infection, some medications, and foods.

Causes of Excessive Sweating

Metabolic Disorders

Some of the metabolic disorders that can cause hyperhidrosis include:

• Hyperthyroidism (overactive thyroid)
• Hyperpituitarism (pituitary disease)
• Hyperglycemia (high blood sugar)
• Hypoglycemia (low blood sugar)
• Pheochromocytoma (benign tumor in the adrenal glands)
• Gout (inflammatory arthritis due to a crystal called uric acid)

Menopause

Menopause can cause increased sweating, especially on the face, as well as generalized hot flashes.

Diabetes

Diabetes mellitus is a chronic disease characterized by high levels of blood glucose, which results when your body doesn’t produce enough insulin or if your cells don’t respond to insulin properly. 

Anxiety

There are several types of anxiety disorders that contribute to excessive sweating. Social anxiety and panic disorder are two examples of such disorders.

Cancer

Many types of cancer can cause hyperhidrosis. These include cancers of the blood, lymphatic system, nervous system, bone, and liver.

Infection

Infections stimulate the body’s immune system resulting in increased temperature (fever) as well as increased sweating.

Certain Medications and Foods

A partial list of medications and foods that can cause hyperhidrosis includes:

• Dopamine agonists: Medications to treat conditions resulting from dopamine loss. Often used to treat Parkinson’s disease and restless leg syndrome.
• Selective serotonin reuptake inhibitors (SSRIs): SSRIs are medications used to treat depression and anxiety by increasing serotonin levels in the brain.
• Antipsychotics: Antipsychotic medications are psychiatric medications used to treat psychosis.
• Insulin: Insulin is a prescription medication to treat diabetes.
• Foods: Acidic foods and spicy foods can cause the body to sweat.

Diagnosis

A healthcare provider can determine if symptoms of increased sweating are due to primary hyperhidrosis or secondary hyperhidrosis. Testing may be needed in order to make a diagnosis.

Some of the tests that may be performed are discussed below.

Blood Tests

Some of the tests performed by your healthcare provider when secondary hyperhidrosis is suspected are: 

• A complete blood count
• A basic metabolic panel
• A thyroid-stimulating hormone test
• A sedimentation rate
• An antinuclear antibody test

These tests help your healthcare provider rule out infections, kidney dysfunction, cancer, diabetes mellitus, thyroid disease, inflammatory disorders, or connective tissue disease.

Starch-Iodine Test

A starch-iodine test (also called the Minor test) is used to determine the areas of the body that are affected by primary hyperhidrosis.

This is a simple, painless test that allows a clinician to actually see areas of increased sweating. This can help determine a specific treatment plan.

Paper Test

Paper filter tests and gravimetry are methods that researchers have used to measure the amount of sweat produced by specific areas of the body. 

Treatment

Topical Agents

Topical antiperspirants are the first-line treatment for underarm sweating. Aluminum salts in antiperspirants irritate the sweat gland and cause it to swell, preventing the sweat from leaving. 

People who sweat excessively generally need antiperspirants with 10–15% aluminum salts.

These are applied at night once or twice a week and may require sleeping with your armpits wrapped in plastic wrap, or wearing gloves on your hands, or wearing socks on your feet. The main side effect is local irritation.

Oral Medication

By reducing the secretion of sweat, oral anticholinergic medications can help people with hyperhidrosis, but these drugs aren’t approved for this purpose by the FDA.

Common side effects of oral anticholinergic medications include:

• Dry mouth
• Constipation
• Impaired taste
• Blurry vision
• Heart palpitations

Botox

Botulinum toxin (Botox) injections are FDA-approved for treating underarm hyperhidrosis, and they also work on hands and feet.

It’s the treatment of choice for marked hyperhidrosis. 

With this treatment, you’ll notice relief within a day or two, and the effects last 6-10 months. Injections in the palms and soles can be painful, but less so in armpits.

Risks include bleeding at the injection site and weakness in the muscles near the injection sites..

Iontophoresis

Iontophoresis is a technique that temporarily blocks the sweat glands.

It consists of placing your hands or feet in lukewarm tap water, allowing a mild electric current to travel through the water and temporarily block the sweat gland. 

The symptoms usually disappear after 5–10 sessions.

The side effects are dry or irritated skin.

This treatment is generally deemed safe, though you shouldn’t undergo the procedure if you’re pregnant or have a heart or electrical device (such as a pacemaker).

Surgery

For more serious cases, surgery (sympathectomy) may be used to cut the sympathetic nerves to the sweat glands, blocking nerve signals from triggering the sweat glands.

When to See a Healthcare Provider

See a healthcare provider if you’re experiencing an impairment in your daily activities due to overactive sweat glands.

Any sweating that interferes with your life should be considered excessive and should be evaluated.

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