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Sweat explained
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Sweat is produced by glands in the deeper layer of the skin, the dermis. Sweat glands occur all over the body, but are most numerous on the forehead, the armpits, the palms and the soles of the feet. Sweat is mainly water, but it also contains some salts. Its main function is to control body temperature. As the water in the sweat evaporates, the surface of the skin cools. An additional function of sweat is to help with gripping, by slightly moistening the palms.
Normal sweating
Normal, healthy sweating is caused by:
- Hot temperatures, such as in summer
- Physical exercise
- Emotional stress
- Eating hot or spicy foods
- Fever associated with illness.
Increased sweating (hyperhidrosis)
Abnormal increased sweating is known as hyperhidrosis. In most cases, the cause of hyperhidrosis is unknown. Some known causes include:
- Obesity
- Hormonal changes associated with menopause (hot flushes)
- Illnesses associated with fever, such as infection or malaria
- An overactive thyroid gland (hyperthyroidism)
- Diabetes
- Certain medications.
Diagnosing increased sweating
In the majority of cases, no investigations are required to diagnose hyperhidrosis. Occasionally a blood test for thyroid disease is recommended.
Idiopathic hyperhidrosis
This is the most common form of excessive sweating. It is called idiopathic because no cause can be found for it. It can develop during childhood or later in life. It can affect any part of the body, but the palms and soles or the armpits are the most commonly affected areas. The excessive sweating may occur even during cool weather, but it is worse during warm weather and when a person is under emotional stress.
Treatment options for excessive sweating
Treatment for excessive sweating depends on the cause. This may include:
- Reducing weight – if obese.
- Medical management – to reduce the hot flushes of menopause.
- Antiperspirant applications – sprays, powders and roll-ons.
- Iontophoresis – the activity of sweat glands is temporarily reduced by passing a low-level electric current through the skin.
- Botox injections – to paralyse sweat glands. The effect from a single injection lasts six to nine months.
- Surgery – to the nerves that control sweat glands may be considered in severe cases where all other treatments have been unsuccessful.
Self-help strategies for managing hyperhidrosis
Some strategies for managing hyperhidrosis at home include:
- Wear loose clothing.
- Use antiperspirants that contain aluminium chloride and are designed for hyperhidrosis – follow the instructions carefully. While advertised mainly for use in the armpits, these agents can also be used on the palms, soles and forehead or wherever the hyperhidrosis occurs.
Reduced sweating
Reduced sweating is called hypohidrosis, if there is partial loss of sweating, or anhidrosis if there is complete lack of sweating. This can occur for a number of reasons, which include:
- Some skin disorders
- Burns to skin that damage the sweat glands
- Underactive thyroid (hypothyroidism)
- Dehydration
- Prolonged excessive heat or exercise during hot weather.
Lack of sweating may create problems of temperature control and lead to steep rises in body temperature during hot weather. Occasionally, this can be life threatening.
Heat stroke and heat exhaustion
Heat stroke (or sun stroke) can occur in hot weather when not enough sweat is produced to keep the body cool. Symptoms can include:
- Muscle cramps
- Headache
- Nausea
- Vomiting.
Excessive loss of body salts and water can lead to a life-threatening complication known as heat exhaustion. Heat stroke can be managed, and heat exhaustion prevented, by seeking a cool, shaded place, drinking plenty of fluids and sponging the body with water, if necessary.
Where to get help
- Your doctor
- A dermatologist.
Things to remember
- Sweat keeps the body cool as it evaporates from the skin.
- Heat stroke occurs when sweat can’t evaporate fast enough to cool the body.
- Hyperhidrosis is excessive sweating.
- Known causes of heavy sweating include obesity, thyroid disease and diabetes.
You might also be interested in:
Heat stress and sport - reducing the risks.
Personal hygiene.
Skin explained.
Want to know more?
Go to More information for support groups, related links and references.
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This page has been produced in consultation with, and approved by:
St Vincent's Hospital - Department of Dermatology
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Copyight © 1999/2009 State of Victoria. Reproduced from the Better Health Channel (www.betterhealth.vic.gov.au) at no cost with permission of the Victorian Minister for Health. Unauthorised reproduction and other uses comprised in the copyright are prohibited without permission.
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This Better Health Channel fact sheet has passed through a rigorous approval process. For the latest updates and more information visit www.betterhealth.vic.gov.au.
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Last updated: February 2009
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Sweat explained - Better Health Channel
The main function of sweat is to control body temperature as it evaporates from the skin. Heat stroke can occur on a hot day if there is insufficient sweating. Hyperhidrosis is abnormal excessive sweating, most often without any known cause. Reduced sweating is called hypohidrosis, if there is partial loss of sweating, or anhidrosis if there is complete lack of sweating...
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Sweat explained - Better Health ChannelThe main function of sweat is to control body temperature as it evaporates from the skin. Heat stroke can occur on a hot day if there is insufficient sweating. Hyperhidrosis is abnormal excessive sweating, most often without any known cause. Reduced sweating is called hypohidrosis, if there is partial loss of sweating, or anhidrosis if there is complete lack of sweating...
© State of Victoria. All rights reserved
The information published here was accurate at the time of publication and is not intended to take the place of medical advice. Please seek advice from a qualified health care professional.
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