Excessive sweating of the feet, a common problem

Plantar hyperhidrosis is defined as localized hypersweating at the arch of the feet, where the skin is dense with sweat glands.

General information on sweat glands

The sweat gland is a skin gland secreting sweat, with a dual role:

• Thermoregulator, by eliminating excess heat from the body;
• Excretory, by eliminating toxins.

We have two types of glands and two types of sweat:

• An apocrine sweat gland is always associated with the pilosebaceous follicles. They are distributed in the genital area and under the arms. Their thick sweat is a mixture of pheromones, water, urea and ammonia.
• An eccrine sweat gland is located on the rest of the body, including the arch of the foot. Their sweat is liquid, odourless, composed mainly of water, lactic acid and mineral salts.

The production of sweat by these glands is dependent on the sympathetic ANS (autonomic nervous system) which manages stress. Although adrenaline is the main neurotransmitter, it is acetylcholine that is found at the end of the chain, which activates sweat secretion.

What is foot hyperhidrosis?

Heavy perspiration affecting the soles of the feet remains a dysfunction that is probably of hereditary origin, but is poorly understood: it is idiopathic plantar hyperhidrosis, often developing during puberty, and decreasing in frequency beyond the age of 40.
More rarely, excessive sweating of the feet is the consequence of another identified disease, and we then speak of secondary plantar hyperhidrosis: hyperthyroidism, diabetic disease, pheochromocytoma, ...

The major clinical sign remains the soles of the feet that sweat excessively and frequently for no reason.
This liquid sweat soaks between the toes. Affected people often feel a cold on their feet, in the middle of a warm atmosphere, because this sweat eliminates the heat that cannot evaporate, accentuating the "sauna" effect in a shoe.
This lack of ventilation is at the origin of secondary signs with proliferation of germs:

• The lactic acid of sweat lowers the pH, which helps the growth of fungi, resulting in more or less circular, often red or white fungal lesions.
• The maceration softens the horny layer epidermis, weakening the skin, from which more frequently ingrown nails, ulcers or blisters appear.
• Moisture contributes to the development of bacteria, which are at the origin of bad smells (bromidrosis) by producing catabolic waste.

It is then when difficulties in the social bond can develop, with shame and embarrassment, leading to physical and then psychological isolation: one is ashamed of body odors and loses self-confidence.

When he studied a disease called botulism, caused by botulinum toxin from Clostridium botulinum, Justinus Kerner had already observed in 1880 that botulism patients did not sweat.
Today we know why. An antiperspirant injection based on botulinum toxin will block the acetyl-choline receptors. Without this neurotransmitter, the sweat gland no longer receives a signal and no longer activates its secretion. The production of sweat stops.
The treatment of plantar hyperhidrosis presupposes beforehand that your aesthetic doctor has assessed how it is a source of suffering or discomfort for you.
It is based on questions derived from the HIC (Hyperhidrosis Impact Questionnaire) or the DLQ (Dermatology Life Quality Index), worldwide references in this field.
In case of suspicion of very localized plantar hyperhidrosis, your practitioner can perform a Minor's test (starch and iodine derivative such as Lugol) to see where the secretion occurs. Most often, however, he or she will perform a global treatment of the soles of the feet.
This foot injection of botulinum toxin requires some expertise to target the medium dermis, because the skin covering of the soles of the feet is thick. The injection should be done neither too much on the surface nor too deep, at the risk of a disappointing result.
For maximum comfort, your practitioner uses a Botox type syringe with a local anesthetic. An anesthetic cream can reinforce the absence of pain.
The Botox injection will show its results after five/ten days, by reducing plantar perspiration, with an average effectiveness of about 6 months.
The bad smell of the feet fades away with perspiration.