What Causes Excessive Sweating (Hyperhidrosis)?

Medically Reviewed by Poonam Sachdev on February 08, 2024
6 min read

Hyperhidrosis is excessive sweating. People who have hyperhidrosis sweat to the point that moisture may literally drip from their hands.

Normally, your sweat glands make perspiration that’s carried to the skin’s surface when the air temperature rises, you get a fever, you’re exercising, or you’re feeling anxious, nervous, or under stress. When those things are no longer an issue, the nerves that signal sweating are put on hold.

For the 1% to 2% of people who have hyperhidrosis, the sweat glands don't shut off. They sweat even when the circumstances don’t call for it: when they’re in air conditioning, or while they’re sitting and watching television. Some people even tell their doctors that they sweat in a swimming pool.

The causes of hyperhidrosis depend on the type of sweating that’s happening. Most times, excessive sweating is harmless. In some cases, doctors don’t know why people sweat too much. In other cases, the causes of hyperhidrosis may be a medical condition.

There are two main types of hyperhidrosis.

  • Primary hyperhidrosis (also called focal or essential hyperhidrosis) causes excessive sweating in the hands, underarms, face, and feet without any known reason.
  • Secondary hyperhidrosis (also called generalized hyperhidrosis) causes excessive sweating all over the body or in a larger area of the body and can be caused by excessive heat as well as a medical condition or medication.

If your sweat glands had an “on” switch, those of someone with primary hyperhidrosis would always be flipped up. 

People with primary hyperhidrosis generally sweat from a certain type of gland called eccrine sweat glands. These glands make up the majority of the 2 million to 4 million sweat glands in your body. Eccrine sweat glands are numerous on the feet, palms, face, and armpits. 

When your body is overheated, when you’re moving around, when you’re feeling emotional, or as a result of hormones, nerves activate the sweat glands. When those nerves overreact, it causes hyperhidrosis. For instance, someone may only need to think of a situation that causes anxiety in order to break out in a sweat.

Doctors aren't sure why people have primary hyperhidrosis, although it may be related to the genes you carry. It's the most common cause of excessive sweating, affecting about 1% to 3% of the population. It usually starts in childhood or the teen years.

Primary hyperhidrosis does not make you sick. Basically, you just sweat too much. Although it's a medical condition, it's not a sign of disease or a drug interaction. If you have it, you'll be otherwise healthy.

The symptoms of primary hyperhidrosis are fairly specific. It's sometimes called focal or localized because it only affects specific parts of the body, such as the underarms, groin, head, face, hands, or feet. Symptoms also tend to be symmetrical, happening on both sides of the body equally. When the excessive sweating is on your hands, it's called palmar hyperhidrosis.

Why does it happen? Experts aren't sure, but primary focal hyperhidrosis seems to stem from a minor malfunction in the sympathetic nervous system. This part of your nervous system acts like a thermostat. It's controlled through a part of the brain known as the hypothalamus. When you're hot, it should signal to sweat glands to make sweat. When you have excessive sweating, your nervous system sends signals to eccrine sweat glands when it shouldn't. There's some evidence that it could run in families. 

People with primary hyperhidrosis may get relief with nonsurgical treatments, including:

  • Over-the-counter or prescription-strength antiperspirants that contain aluminum salts or aluminum chloride
  • Medications called anticholinergics that affect the nerve signals to sweat glands. You may take them in pill form or apply them to your skin as a cream or with a medicated wipe.
  • A low-intensity electrical current treatment called iontophoresis
  • Botox injections for underarm sweating
  • Anxiety medications to manage the stress than can cause you to sweat

Surgery is usually only considered as a last resort for people with severe sweating in their hands and underarms. Surgery may involve removing sweat glands from the area. During another procedure, called thoracic sympathectomy, a surgeon cuts and destroys the nerves responsible for sweating.

One common side effect is excessive sweating in other parts of the body, such as the chest, back, or legs. Other possible risks include bleeding into the chest and nerve problems.

This less common form of hyperhidrosis causes sweating all over the body – not just on the hands or feet. Secondary general hyperhidrosis is also more serious medically. It's called secondary because it's being caused by something else, such as another health condition.

One telltale sign of secondary hyperhidrosis is excessive generalized sweating at night. One reason it happens is that your immune system is in high gear. Conditions that come with lots of inflammation, such as rheumatoid arthritis (RA), can cause this.

What else can trigger secondary general hyperhidrosis? There are many possibilities, including medical conditions and diseases. They include:

  • Menopause
  • Pregnancy
  • Thyroid problems
  • Diabetes
  • Alcoholism
  • Infectious diseases like tuberculosis
  • Parkinson's disease
  • Rheumatoid arthritis
  • Stroke
  • Heart failure
  • Cancers like leukemia and lymphoma

Medications can also cause general excessive sweating. Medications that can cause sweating include:

  • Some psychiatric drugs
  • Some blood pressure medications
  • Some medicines for dry mouth
  • Some antibiotics
  • Some supplements

Many medications can also cause excessive sweating. Tell your doctor if you take:

RA hyperhidrosis causes

Conditions like RA can make your immune system too active. Your body will have inflammation in your joints and other places. This constant inflammation when you're in a flare can come with hyperhidrosis and night sweats.

Asymmetric hyperhidrosis causes

Excessive sweating usually happens the same on both sides of your body. When it doesn't, it's called asymmetric hyperhidrosis. This type of excessive sweating suggests there's a problem in your nervous system. When the cause is related to hormones, medicine, cancer, infection, or other things that affect your whole body, the sweating will usually be general and all over your body.

Anxiety hyperhidrosis causes

When you're anxious – or have an anxiety disorder – you may sweat more than other people. But anxious sweating isn't the same as hyperhidrosis. It's possible to have hyperhidrosis and anxious sweating at the same time.

Uncovering the medical condition that's causing your hyperhidrosis and getting the proper treatment for it will help lessen the sweating of secondary hyperhidrosis. That’s why it’s best to tell your doctor when you’re having a problem with sweating, so that you can uncover the reasons behind it and get it treated.

Hyperhidrosis or excessive sweating can happen for lots of reasons. Sometimes doctors may be able to figure out why it's happening and help you find ways to stop it. Many other times, there's no clear cause and you'll need to manage the extra sweat in other ways. If you are struggling with excessive sweat, talk to a doctor to see if you can find out the cause and ways to make it better.

  • What causes palmar hyperhidrosis?

Palmar hyperhidrosis or sweaty palms is a type of primary hyperhidrosis. It happens when your sweat glands are overactive. It could be related to the genes you carry and often runs in families, but doctors may not be able to tell you an exact cause.

  • Is hyperhidrosis genetic?

Primary hyperhidrosis does seem to run in families. If you have excessive sweating for reasons that aren't clear, it may be genetic.

  • What causes craniofacial hyperhidrosis?

If your face and head sweat too much, it may be because your sweat glands are overreacting for reasons that aren't clear. But excess sweating of your face also can happen from other conditions, such as Horner's syndrome, sweating during eating (gustatory sweating), headache, Harlequin syndrome, or menopause.