Sweating Treatment Side Effects: Hand Weakness, Numbness, Burns

What side effects occur after treatment for sweating?

Aesthetic centres most often offer three methods for excessive sweating (hyperhidrosis): botulinum toxin injections into the skin, microwave thermolysis devices that damage the sweat glands in the armpit with heat, and iontophoresis for the hands and feet (passing a weak electric current through water). Each has a different side effect profile. What they have in common is that most problems are limited to the treated area and are temporary.

This article does not describe again how the methods are carried out or who they are suitable for; for that, see our article “Treatment of Excessive Sweating (Hyperhidrosis)”. Here, we aim to help you tell which symptoms after the treatment are expected, which call for consulting your physician and which are an emergency. Side effects specific to botulinum toxin treatments in the face (such as a drooping eyelid or brow asymmetry) are described in detail in our article “Side Effects after Botulinum Toxin”.

Side effects of underarm botulinum toxin: what can you expect?

Botulinum toxin in the armpits is the most studied treatment for excessive sweating. In a large, placebo-controlled study on this subject, the proportion of people reporting side effects was 11 per cent in the medicine group and 5 per cent in the placebo group; the difference was not statistically significant. In other words, most people did not experience a significant side effect. Unlike in the face, problems affecting the eyelids or the muscles of facial expression are not expected in the armpit. The very rare symptoms of the medicine spreading to distant areas, however, are equally urgent in every area; if there is difficulty swallowing, speaking or breathing, call 112 (or your local emergency number).

• Pain and tenderness at the needle points: expected because many small injections are given; usually decreases the same day or within a few days.
• Small bruises and mild itching: usually pass on their own.
• Headache and muscle pain: reported uncommonly, mostly short-lived.
• Mild pain or a feeling of tiredness in the arm muscles: may occur briefly in muscles close to the injection area.
• Infection: uncommon; redness, warmth and discharge that increase over the days are a reason to see a physician. For details, see our article “Infection after Aesthetic Treatments”.

Why does hand weakness occur after palm botulinum toxin, and how long does it last?

The skin of the palm is thin, and the small hand muscles beneath it lie close to the skin. Some of the medicine injected into the skin can reach these muscles and temporarily weaken the fine movements of the fingers. In a small study of 24 people, hand grip strength did not change, whereas pinch strength between two fingers (for example holding a key with the fingertips) had decreased markedly after two weeks; the decrease was greater in the higher-dose group. Strength improved over time but was still measured slightly lower than at the start even after six months. This study is small, and the results cannot be generalised to every treatment.

For most people this weakness does not prevent daily tasks, but it is noticeable in some activities. So before palm treatment, if your work requires manual dexterity or you have an exam or an important work schedule, it is useful to discuss the timing with your physician. The palm is also a sensitive area, and the treatment is more painful than in the armpit; ask in advance about ways to reduce the pain.

• Situations where it may be noticed: buttoning clothes, holding a pen, typing on a phone, opening a jar, playing a musical instrument, fine handiwork.
• If you notice reduced strength in your hand, note the tasks you find difficult and describe them to your physician at the follow-up; the physician can change the plan for the next treatment accordingly.
• If there is weakness not only in the hand but also in the arm or neck, or in swallowing or speaking, this is not a local effect; get emergency help without waiting.
• If reduced strength in the hand is accompanied by numbness, a bluish discolouration or coldness, this is not an expected effect; contact your physician the same day.

Treatment of the soles of the feet: pain and discomfort when walking

Like the palm, the sole of the foot is a sensitive area; the treatment can be painful, and in the first days there may be pressure-related tenderness and discomfort when walking. The British Association of Dermatologists states that botulinum toxin in the palms and soles can cause temporary weakness in the hand and foot muscles and is painful, which is why it is not often used in these areas. Studies on use in the soles of the feet are limited; the effect may last for a shorter time than in the armpit.

Does botulinum toxin for sweating cause more sweating elsewhere?

Compensatory sweating is a marked increase in sweating in other parts of the body when sweating decreases in the treated area. In the sources, this problem is mainly associated with sympathectomy surgery (a procedure on the chain of nerves in the chest cavity that controls sweating); after this surgery, most people develop some compensatory sweating, seen on the abdomen, back or legs.

Marked compensatory sweating is not described as a typical side effect of botulinum toxin, microwave thermolysis or iontophoresis in the sources we reviewed. Some people say they feel they sweat more on the back or chest after underarm treatment; it is not well known whether this is a real increase or a shift of attention to the areas that still sweat. Because the effect of botulinum toxin is temporary, even if there is such a change, it is expected to disappear as the effect wears off. If new sweating in other areas becomes marked enough to disrupt daily life, consult your physician so that they can check whether there is another cause.

Swelling, numbness and nerve involvement after microwave thermolysis

Microwave thermolysis is a device treatment that damages the sweat glands beneath the skin of the armpit with heat. Because damaged sweat glands do not form again, its effect, unlike that of botulinum toxin, is not temporary; this makes the side effects and the decision important. In a small study comparing it with botulinum toxin in the armpit, the two methods produced a similar reduction in sweating after one year; a reduction in underarm hair was also seen on the microwave side.

• Expected: swelling, tenderness, pain and a feeling of firmness to the touch in the armpit after the treatment. Mostly decreases within days.
• Marks from the suction head: temporary red marks may remain where the device drew the skin towards it.
• Change in sensation: temporary numbness or tingling in the skin of the armpit or the inner side of the arm has been reported.
• Colour change and burns: the American Academy of Dermatology lists colour change and, more seriously, burns and long-lasting nerve pain among the possible side effects.

A rare but serious situation is involvement of the nerves in the arm. Case reports describe people who developed loss of sensation and loss of strength in the arm and hand after the treatment; in one reported case, there was no complete recovery despite six months of physiotherapy. The authors of the report recommended starting with a lower energy in slim people with little fatty tissue in the armpit. How often these cases occur is not known. If you notice numbness, weakness or electric-shock-like pain in your arm, hand or fingers after the treatment, report it to your physician the same day rather than waiting for it to pass.

Iontophoresis: tingling, burning and skin irritation

Iontophoresis is generally a well-tolerated method. In a small, controlled study in palm sweating, only one person had a local side effect during two weeks of treatment. The American Academy of Dermatology states that a mild burning or tingling sensation may occur while the device is in use and that a mild burn may develop if it is used incorrectly.

• A tingling, prickling or mild burning sensation can be expected during the session; if the pain becomes unbearable, stop the session and discuss the settings with your physician.
• If there is a small cut or crack in the skin, the current can concentrate at that point and cause more burning.
• Dryness, redness or flaking may be seen after the session.
• An area that blisters, crusts or does not heal within days may be a burn; show it to your physician before starting a new session.
• If you have a pacemaker or a metal implant in your body, or are pregnant, be sure to tell your physician before iontophoresis.

Which problems stand out with which method?

Should your sweating be medically investigated first?

Most people with excessive sweating have no underlying disease; this is called primary hyperhidrosis and usually occurs symmetrically on both sides in the armpits, palms, soles or face. However, sweating can also be the result of a disease or a medicine being taken (secondary hyperhidrosis). In that case, even if an aesthetic treatment reduces the sweating for a while, it can mask the real cause. International sources regard ruling out secondary causes as the first step before treatment.

If you have one of the features below, ask your physician to assess your sweating before an aesthetic treatment. These features do not mean that you have a disease; they only show that it should be investigated.

• Widespread sweating all over the body, not limited to certain areas
• Sweating on one side only or with an irregular distribution
• Sweating that starts for the first time in adulthood without an obvious cause
• Night sweats that wake you up and soak the sheets
• Sweating accompanied by weight loss, fever, palpitations, trembling or fatigue
• Sweating that appears after starting a new medicine (do not stop your medicine yourself; consult your physician)

If necessary, your physician may request tests such as blood sugar or thyroid tests. For how the medicines you take interact with procedures, our article “Medical Aesthetics for People on Medication or with Chronic Conditions” can be a useful guide.

What should you do if you notice a problem?

1. Note when the symptom started, after which treatment it occurred and whether it is decreasing; if an area is changing, photograph it every day in the same light.
2. After palm treatment, write down specifically the tasks you find difficult (for example buttoning clothes, holding a pen).
3. In situations such as numbness or loss of strength in the arm, a burn that blisters, or increasing redness and discharge, contact the physician who performed the treatment the same day.
4. Unless your physician recommends it, do not apply heat, massage, home remedies or over-the-counter creams to the area.
5. If you cannot reach the centre that performed the treatment, go to a dermatology outpatient clinic or an emergency department with your treatment details. For a step-by-step approach, see our article “What Should You Do If a Complication Occurs after an Aesthetic Treatment?”.

An honest note on the evidence

Most studies on treatments for excessive sweating are small and have been carried out with different methods. A comprehensive review carried out in England stated that the overall evidence is limited and that the strongest evidence exists for botulinum toxin in the armpits. For palm and sole treatments, microwave thermolysis and iontophoresis, the frequency of side effects is not known with certainty. Some of the serious side effects related to devices have been learned only from individual case reports. So before the treatment, ask your physician to explain clearly the possible side effects of the method recommended to you and how you will be followed up if a problem arises.

This content is for information only; it does not replace an examination. The meaning of your symptoms and the treatment that suits you can only be determined by a physician’s assessment.