Approximately 4 million sweat glands cover the body and produce the clear liquid that we know as sweat. The body produces sweat to help regulate its temperature. Certain triggers can cause us to sweat, including warm temperatures, exercise, nervousness, fear, or embarrassment. In people with hyperhidrosis, the amount of sweat produced is greater than normal and may occur even when the surrounding temperature is cool.

Hyperhidrosis usually happens in people aged 25 to 64, although younger people may also be affected. Interruptions to daily activities as well as other social disruptions caused by excess sweat are a common result of this condition. In some cases, people don't seek treatment from a doctor because they do not realize that treatment exists to reduce the amount of sweat a person produces.

The cause of hyperhidrosis is overactive sweat glands. There are two types of hyperhidrosis: generalized and focal.

In generalized hyperhidrosis (also known as secondary hyperhidrosis), excessive sweating occurs over the entire body. It is often caused by a medical condition such as an infection, a chronic disease, or a disorder that disrupts the body's natural balance of hormones. It may also be caused by medications (e.g., antidepressants).

Focal hyperhidrosis (also known as primary hyperhidrosis) occurs on a specific part of the body including the armpits, soles of the feet, palms of hands, face, or other areas. Genetics play a role as many people with focal hyperhidrosis have other family members with the condition. Hyperhidrosis is not a contagious condition.

Excessive sweating is the main symptom of hyperhidrosis. It may affect the entire body or just certain body areas, such as the armpits, hands, face, or feet.

Because it causes increased wetness on the surface of the hands, the face, and other areas of the body, this condition may significantly affect a person's social life and workplace activities.

Many people feel self-conscious about shaking hands or hugging, and may avoid physical activity because it makes them sweat. Feelings of embarrassment and humiliation are common. The excessive sweating may also interfere with a person's ability to do their job.

To make the diagnosis, your doctor will perform a physical examination to determine the presence of sweat, and will usually do medical tests to rule out any underlying conditions that might be causing generalized hyperhidrosis. 

Focal hyperhidrosis can be diagnosed if you have unexplained, visible, excessive sweating in areas like the armpits, hands, face, or feet for at least 6 months and at least 2 of the following criteria:

• excessive sweating happens more than once per week
• if you have a family member who has been diagnosed with focal hyperhidrosis
• the sweating is about the same on both sides of the body
• the sweating stops during sleep
• your symptoms are affecting your ability to perform daily activities
• your symptoms began before the age of 25

Simple tests to confirm the condition may also be used. Two common tests include:

• starch iodine test: A doctor applies iodine solution to the sweaty area and then sprinkles starch to look for a dark blue or purple colour. This colour indicates the area of excess sweat.
• paper test: A doctor places special paper on the area where sweating is observed. Sweat absorbs into the paper and then the paper is weighed. The weight of the paper after the test indicates how much sweat was absorbed.

Various types of treatment are available, in particular for focal or localized hyperhidrosis.

The main forms of treatment include:

• topical medications (applied to skin): Topical medications contain aluminum salts in higher concentrations than those found in regular antiperspirants. They are used to treat mild forms of hyperhidrosis. Some irritation may occur with this type of treatment including burning or stinging.
• oral medications: Certain medications that reduce sweating by affecting the cholinergic nerves may be recommended. Side effects associated with these medications include dry mouth, constipation, increased heart rate, urinary difficulties, sedation, and blurry vision.
• botulinum toxin A: This treatment is used for focal hyperhidrosis in the armpit area or on the palms. Treatment involves injecting the affected area with a chemical that blocks the signal from the nerve to the sweat gland. Injections are made into the skin (intradermal) every several months. Side effects include pain at the injection site, itching, and headache.
• surgical procedures: Surgical destruction or disruption of nerve pathways that cause sweat glands to produce sweat may be used for people who do not respond well to other treatments. Risks of the surgery include infection, bleeding, and nerve damage. There is also the risk of compensatory hyperhidrosis, in which the patient sweats from a different area after the surgery.
• iontophoresis: In this form of treatment, the affected area is submerged in water and an electric current is passed through the water. It is unclear exactly how this treatment works; however, the electrical charge may affect the production of sweat from glands. This method is time-consuming and requires several weeks of treatment to reach normal levels of sweating. Side effects include dry, peeling skin.