Sweating is a physiological phenomenon of our body that maintains body temperature at stable values (37 °C): by evaporating, sweating consumes heat that is taken away from the body, allowing to dispose of thermal energy and thus to protect the biological stability of the body. In the human body this mechanism is regulated (in the peripheral areas) by the autonomous nervous system, more precisely by the sympathetic system: the regulatory center of sweating is located at the level of the preoptic area and the anterior hypothalamus contains the neurons that are responsible for maintaining the thermal balance. The sweat glands are innervated by cholinergic asbestos C-fibers, and in the human body they are present in two main forms, the apocrine and the eccrine. The apocrine glands are found only in some body districts (armpits, areola mammaria, ano-genital region and external acoustic meato); the production of apocrine sweat is scarce and does not contribute substantially to thermoregulation, so it does not affect even hypersuduation. The eccrine glands, on the contrary, are distributed over the whole cutaneous surface but are not found in the mucous membranes: it is thought that their number amounts to about 2-4 millions, with an average density varying depending on the body surface (most of them are concentrated at the level of the palm surfaces).
Sweat is a clear, hypotonic liquid, with a pH between 4 and 6.8: it contains salts, urea, lactate, but also potassium, bicarbonate, calcium and in smaller quantities glucose, amino acids and proteins, and is an important constituent of the hydrolipidic film of the skin. The production of sweat is continuous and normally unnoticeable (perspiratio insensibilis), while it becomes evident in response to thermal, intrapsychic (intellectual and emotional) and gustatory stimuli (resulting from the ingestion of particular foods); local temperature, hormones, changes in the vascular circulation and osmolarity, axonic and spinal reflexes still regulate sweating. The functionality of the sweat glands can be evaluated by means of various techniques: some, such as the intraductal insertion of microcannulae and the measurement of the volume of sweat collected in special containers at rest or after appropriate stimuli (thermal, with acetylcholine, with pilocarpine), are quite complex, others, such as the direct display of sweat with direct microscopy, imprints of detection of plastic or silicone and especially colorimetric techniques, are instead easier and are used more frequently in clinical practice.
Hypersudoration (but the scientific term is hyperhidrosis) can be defined as excessive sweating which is generally, but not always, necessary to maintain the thermal balance. Normally a quantity of sweat of about 0.5-1 ml/min is produced, but under conditions of marked thermal stress it can even reach 10-12 l per day; therefore there are slight, moderate or intense manifestations of the disorder, which in the moderate/intense form seems to affect at least 3% of the general population, in particular people between 25 and 64 years of age.
Hyperhidrosis is a condition that brings considerable discomfort to the individual who is affected: it mainly occurs at the level of the hands, feet and armpits, with levels of sweating that can vary up to the drip. Anxiety is a triggering factor and this contributes to considerable social embarrassment and in the context of affective relationships; some subjects even manage to avoid any social contact. Hypersudoration can cause problems of a professional nature, especially in subjects who handle paper or fabrics on which sweat marks may remain, and sensations of strong discomfort, for example in the case of axillary hypersudoration, due to the large stains of sweat in the armpits and back of t-shirts, shirts or jackets, also generating an impression of neglect of the ‘individual.
The therapy of secondary hypersuduation must be aimed at resolving the causal pathological condition. Symptomatic therapy is indicated not only in patients with essential hypersudoration, but also in those affected by the secondary form, especially if they do not respond to causal therapy, and also in psychiatric patients, where the disorder is not only a consequence, but often an aggravating factor of emotional instability.
The therapeutic management of idiopathic hypersurvey is rather difficult and includes various possible treatments, many of which have limited or doubtful efficacy or poor tolerability. Hypersudoration, however, should be considered an annoying but essentially benign condition. The reduction of sweating can also have important pathological implications because, if marked or complete (anhydrosis) it can cause hyperthermia and heat stroke. To avoid these fearsome complications, appropriate preventive measures must be taken.
The main approaches are described below.
Topical antiperspirants are the first choice therapy: the most effective substance seems to be aluminum chloride, which however involves a regular repetition of the treatment and in some patients can cause irritative reactions of the skin; other substances, more rarely used, are the salts of zirconium or zinc, aldehydes (glutaraldehyde), formalin and tannic acid. The use of some is limited by the fact that they can cause contact dermatitis, hyperpigmentation of the skin and damage to clothing.
Iontophoresis consists of applying a low-intensity direct current by means of a direct current generator to the palms of the hands or to the soles of the feet immersed in an electrolytic solution. The current obstructs the sweat gland ducts for a limited period, so it should be repeated regularly. This method is usually considered after the failure of the antiperspirant treatment.
Those administered orally (atropine, glycopyrrolate) reduce sweating but are associated with frequent and poorly tolerated side effects, such as dry mouth, vision problems, mydriasis, tachycardia and difficulty in urination; topical anticholinergics (glycopyrrolate, etc.) can on the other hand be absorbed at a systemic level.
Other oral drugs This category includes: amitriptyline, clonazepam, clonidine, diltiazem, indomethacin, gabapentin, propanolol.
Multiple subdermal injections are made with minimal amounts of toxin, so that the affected area is evenly covered. The inhibitory effect lasts for about 5-8 months, with excellent results.