Botulinum toxin, a solution for excessive perspiration?

What is hyperhidrosis?

Perspiration is a vital natural phenomenon for regulating body temperature. During physical activity, intense heat, or a fever, the body produces sweat through the sweat glands. This mechanism allows us to regulate body temperature . While perspiration is natural, it is produced excessively in some individuals. This excess is called hyperhidrosis. It most often affects the armpits, palms, and soles of the feet . Hyperhidrosis can be hereditary, but it can also be triggered by other factors such as certain medications, pregnancy, pre-menopause, or thyroid problems. If this excessive sweating is not treated, it can in some cases cause maceration and lead to secondary microbial infections.

Botulinum toxin as a solution for excessive perspiration?

Botulinum toxin appears, according to scientific literature, to be one of the most effective treatments for regulating excessive perspiration. This molecule is naturally produced by a bacterium called Clostridium botulinum. Botulinum toxin works by blocking the release of acetylcholine, a neurotransmitter responsible for activating the sweat glands. Normally, when the body perceives a thermoregulation or stress signal, acetylcholine stimulates these glands to produce sweat. By injecting botulinum toxin into the affected areas (armpits, palms, feet, forehead), it temporarily inhibits this nerve transmission, thus preventing the overproduction of sweat. The effect appears after a few days and usually lasts several months before the activity of the sweat glands gradually resumes.

A survey conducted on 1985 individuals suffering from excessive sweating has highlighted the effectiveness of botulinum toxin injections as a treatment. The results indicated that 87.6 % of patients suffering from hyperhidrosis preferred botulinum toxin injections in terms of effectiveness compared to traditional antiperspirants, suggesting that this treatment appears to be the most effective against hyperhidrosis.

How does the process of botulinum toxin injections unfold?

Botulinum toxin injections are used as a second-line treatment when topical treatments, often based on aluminium salts, have not worked. The molecules are injected under the skin with extremely fine needles. The injections can be administered to various parts of the body, such as the forehead, armpits, hands, and feet. The patient may experience slight discomfort as multiple injections are required to cover the treatment area. For instance, for the armpits, about fifteen injections are needed for each side. As for the hand, the patient may receive up to 40 injections. In this case, a numbing cream is applied.

A multicentre trial was conducted on 145 patients suffering from hyperhidrosis to assess the effectiveness of botulinum toxin A injections. In each participant, 200 units of botulinum toxin A were injected into one armpit, while the other armpit received a placebo. Two weeks later, once the treatments were revealed, the armpit initially treated with placebo received an injection of 100 units of botulinum toxin A in turn. The reduction in perspiration was measured by gravimetry, a method that quantifies the sweat produced.

The results showed that an injection of 100 units of botulinum toxin led to a reduction in perspiration of more than 25% in 95% of patients, compared to only 35% for the placebo, two weeks after treatment. Furthermore, a reduction of more than 75% in perspiration was observed in 68.3% of treated patients, compared to only 2.8% in the placebo group. Moreover, although the differences were moderate, the results obtained with 200 units of botulinum toxin proved slightly more effective than with 100 units, confirming a dose-dependent trend in symptom improvement.

The effects are not immediate: although some patients notice an improvement from the second day, the maximum effectiveness is typically reached after three months. The number of sessions required varies among individuals. For areas such as the underarms or palms, a session lasts on average 20 minutes. The results generally last for about 7 months.

What are the contraindications and side effects of botulinum toxin injections?

Following the session, the patient may experience slight discomfort. Swelling, muscle weakness, headaches, or even dry mouth may also occur. In an individual who sweats normally, blocking the action of the sweat glands does not present any side effects. However, in those prone to excessive sweating, if perspiration is blocked in certain areas of the body, this production is compensated in other parts. Therefore, treatment with botulinum toxin requires regular monitoring. However, it is crucial not to block too large an area of sweat glands, as perspiration is a vital physiological function for thermoregulation and the elimination of certain toxins. If too large a portion of the sweat glands is inhibited, this could disrupt this natural process and lead to undesirable effects such as overheating of the body like hyperthermia, feelings of discomfort, or imbalances in the body's thermal regulation.

Furthermore, botulinum toxin injections are contraindicated for pregnant and breastfeeding women. Although the effects of botulinum toxin on pregnancy and breastfeeding are not fully established, the lack of sufficient data on its safety for the foetus or infant warrants caution. They are also to be avoided in individuals with a neuromuscular disease. Indeed, the botulinum toxin works by blocking the release of acetylcholine at the neuromuscular junction, which temporarily inhibits muscle activity. In individuals with neuromuscular diseases where the communication between nerves and muscles is already impaired, the injection of botulinum toxin can exacerbate muscle weakness and worsen symptoms. Degenerative diseases and autoimmune diseases, such as multiple sclerosis or lupus, affect the nervous or immune system. The injection of botulinum toxin can interfere with the already fragile balance of the nervous system or trigger an undesirable immune response.