Excessive sweating : a disrupted physiological function
Sweating is a natural process essential to the body's thermal balance. It is carried out by two types of sweat glands : eccrine glands, distributed throughout the skin, which produce watery sweat to release heat, and apocrine glands, located particularly in the underarms and groin, which secrete thicker sweat often associated with body odour.
In hyperhidrosis, this regulatory mechanism becomes disrupted, for no apparent reason or to a disproportionate degree. The sympathetic nervous system, which controls sweat secretion through acetylcholine, becomes overactive, stimulating the glands inappropriately. This results in heavy, sometimes uncontrollable sweating, localised or widespread, occurring independently of weather conditions or physical activity.
Which organ regulates sweating ?
Sweating is regulated by a coordinated group of organs and nerve circuits, led by the hypothalamus. This structure, located at the base of the brain, acts as an internal thermostat. It continually receives signals about body temperature and the environment (heat, emotion, activity), and adjusts the sweating response accordingly.
The hypothalamus sends instructions through the sympathetic autonomic nervous system, which stimulates the eccrine sweat glands distributed throughout the dermis. In response to acetylcholine released at nerve endings, these glands secrete sweat onto the skin's surface.
It is important to note that, unlike most structures supplied by the sympathetic nervous system, sweat glands are activated not by adrenaline but by acetylcholine, a so-called “parasympathetic” neurotransmitter. This neurobiological characteristic partly explains the opportunities for targeted treatment, particularly with botulinum toxin, which is indicated exclusively for primary axillary hyperhidrosis.
The different forms of hyperhidrosis
Two main clinical entities should be distinguished : primary hyperhidrosis and secondary hyperhidrosis.
Primary, or essential, hyperhidrosis is the most common. It begins in adolescence or early adulthood without an identifiable underlying condition. It is generally focal, meaning limited to specific body areas : the palms, soles, underarms, face or even scalp. This form is often symmetrical, bilateral and worsened by stress or emotion, and does not occur during sleep. There is frequently a hereditary component, suggesting a genetic predisposition.
Secondary hyperhidrosis develops later, sometimes suddenly. It is generally widespread and results from an identifiable medical disorder : an endocrine condition (hyperthyroidism, diabetes, phaeochromocytoma), chronic infectious disease (tuberculosis, HIV), paraneoplastic syndrome (lymphoma), or an adverse effect of medicines (antidepressants, glucose-lowering medicines, opioids). This form requires a thorough investigation of its cause, as treatment depends primarily on addressing the underlying condition.
An underestimated functional impairment
Far from being trivial, hyperhidrosis can become socially disabling. It affects interpersonal relationships, self-image and professional life, and in some cases causes considerable psychological withdrawal. Patients with hyperhidrosis avoid physical contact, change their clothing choices, dread oral presentations or handshakes and sometimes develop anticipatory anxiety that worsens the condition.
Alongside the emotional impact, hyperhidrosis causes tangible physical difficulties : skin maceration, irritation, fungal or bacterial infections, difficulty gripping, slipping inside shoes, or disruption of make-up and hairstyles. Yet many patients hesitate to discuss it with their doctor because they are unaware of available treatments or feel ashamed.
A primarily clinical diagnosis
Hyperhidrosis is diagnosed mainly through medical history and clinical examination. The doctor seeks to clarify the onset, pattern, locations and circumstances of excessive sweating. Validated questionnaires, such as the HDSS (Hyperhidrosis Disease Severity Scale), assess the difficulties perceived by the patient.
In secondary hyperhidrosis, further investigations may be indicated : hormone tests, screening for infection, chest or abdominal CT scans, depending on the clinical findings. The Minor test, using iodine and starch, objectively visualises areas of excessive sweating, particularly before botulinum toxin treatment.
Excessive sweating : a common condition
Hyperhidrosis is thought to affect up to 3 % of the general population across all ages. Yet fewer than one in four patients seek advice about it spontaneously. Lack of awareness of treatment options, the personal nature of the symptom and society's tendency to dismiss sweating partly explain this delay in seeking care.
Doctors should ask patients about excessive sweating, especially when it affects quality of life. Patients, for their part, should know that practical, safe and effective solutions are now available to restore both comfort and self-confidence.
Can hyperhidrosis disappear over time ?
In most cases, primary hyperhidrosis – meaning it is not linked to any underlying condition – does not disappear spontaneously over time. Although it may fluctuate during different life stages (puberty, stress, hormonal changes), it tends to persist into adulthood and sometimes worsens without treatment.
However, some patients notice a gradual improvement with age, particularly around their forties, when sympathetic nervous system activity decreases slightly. This nevertheless remains unpredictable and does not occur in everyone. In secondary hyperhidrosis, linked to an identified medical cause (a thyroid disorder or medicine effect, for example), the condition may disappear when the cause is treated.
It is therefore inadvisable to wait for it to disappear : early care markedly improves everyday comfort and prevents lasting psychological effects.
Hyperhidrosis : is it hereditary ?
Primary hyperhidrosis has a well-established hereditary component, although the precise genetic mechanisms are not yet fully understood. An estimated 30 to 50 % of affected people have an immediate family member (parent, brother or sister) with the same condition.
This is not a classic Mendelian pattern of inheritance, but probably a polygenic one, with both genetic and environmental influences. The expression of the condition can vary between patients : some members of the same family may have axillary hyperhidrosis, others a palmar or craniofacial form.
The hereditary component explains why hyperhidrosis can appear in adolescence or early adulthood without any organic disease. However, having an affected parent does not automatically mean developing the condition. Factors such as emotional environment, stress levels or hormonal profile may also influence its clinical expression.
Is excessive sweating dangerous for your health ?
Although disabling, hyperhidrosis is not in itself dangerous to general health. Excessive sweating does not indicate excessive cardiac, renal or metabolic activity. It does not cause chronic dehydration or electrolyte depletion, at least in moderate forms.
However, it can cause skin complications :
- Skin maceration, particularly in folds (underarms, groin folds).
- Fungal infections, particularly between the toes and on the soles.
- Chronic irritation, contact eczema, dermatitis.
- Risk of secondary bacterial infections on damaged skin.
It also causes considerable psychological distress, leading to social anxiety, withdrawal and sometimes a major impact on work or personal relationships. This is why, although not life-threatening, hyperhidrosis deserves active medical care, if only to preserve self-esteem and quality of life.
Can exercise or diet worsen hyperhidrosis ?
Exercise naturally stimulates sweating to regulate temperature. However, in patients with hyperhidrosis, this response may become disproportionate or uncomfortable. This does not mean exercise should be avoided, quite the opposite, good physical fitness improves regulation of the autonomic nervous response and may even improve emotional tolerance of the condition.
Regarding diet, certain foods or stimulating substances can occasionally increase sweating : spices, coffee, tea and caffeinated drinks, alcohol, very hot meals.
For established hyperhidrosis, avoiding these foods during flare-ups or before challenging social situations may be sensible. A balanced diet and adequate hydration support better adaptation of the sweating system.
