A CURE FOR B.O.
Science could make deodorant obsolete
Sweat is a daily nuisance to many people, but to some, the moisture and smell is invalidating. Now, doctors can reduce the sweat production using microwaves and get rid of bad smells by transferring sweat from another person.
The man has not washed his armpits for days. His old sweat gives nourishment to millions of bacteria, which reproduce uncontrollably. The doctor takes a spatula, presses it against the man’s armpit and scrapes off a mixture of dead skin cells, bacteria and sweat. Then, she asks another person – the patient – to lift his arm and wipes it all off in his armpit.
This treatment may sound repulsive, but even a few days later, the patient will probably thank both the doctor and the sweaty man. The bacteria from the donor’s armpits are benign and will not make the sweat smell badly, and right now, they are working hard to settle in the patient’s armpits. Within a short time, they will have won over the person’s own bacteria, which made his sweat smell, and this marks the end of the humiliation of seeing people turning up their noses and pulling away.
The so-called sweat transplant is just one of several new methods to treat profuse sweating. The bad smell is fought using good bacteria, and the amount of sweat can be reduced using nerve poison and microwaves. Most recently, Chinese scientists have discovered a gene, which may give new knowledge about sweat and be the key to new and more efficient treatments of sweat.
EVAPORATED SWEAT COOLS BODY
Sweat is crucial for our survival, as this is the most important way we regulate our body temperature. Under a scorching sun, or working out in the fitness centre, the body gets warm and begins to produce sweat. When the sweat lies on the skin, the body heats it up, making it evaporate. Thus, the sweat takes the heat up into the air, and the body is cooled down. If, however, you wipe off the sweat with a towel, or it drips off by itself, no evaporation takes place, and thus no cooling. As a result, the body produces more sweat in an attempt to keep down the body temperature.
Sweat production is controlled, among other things, by a small area in the lower part of the brain called the hypothalamus. This area works as a kind of thermostat, which measures the temperature of the blood that flows through the brain. If the temperature is too high, the hypothalamus sends out nerve signals to the 2-4 million sweat glands, which can be found in the skin practically all over the body – they are only missing on the lips, the foreskin and labia minora as well as glans on the penis and clitoris. The nerve signal cause the sweat glands to produce sweat.
But it is not only the increased body temperature that makes us sweat. Stress, anxiety, nervousness, pain and other strong, negative feelings make the limbic system in the brain activate the sweat glands. We talk about “the cold sweat of anxiety” or about “breaking a sweat”, and most people have experienced getting sweaty palms in a stressful situation, e.g. on a first date.
The reason is debated, but slightly damp palms may serve to give us a better grip, and from an evolutionary perspective, this may have been an advantage in stressful situations when our ancestors were hunting wild animals or climbing rocky slopes. But when sweating becomes excessive, the sweaty palms have the exact opposite effect.
LIE DETECTOR MEASURES SWEAT
Attacks of sweating caused by emotions happen automatically and cannot be controlled consciously. The police, e.g. in the US, have learned to use this. Sometimes, the authorities use lie detectors, which measure the amount of sweat from the suspect’s palms and fingertips etc. during questioning. An untruthful answer to a question like “Did you shoot your girlfriend?” will unavoidably trigger a stress reaction, which will make the sweat break.
In principle, lie detectors are very reliable, as it is almost impossible to lie without increasing your sweat production. One problem is that the sweat may also be caused by fear of a wrongful conviction.
RUNNER SWEATED THREE LITRES/HOUR
Many of us are familiar with the unpleasant smell of sweat and wet patches under our arms, and studies have shown that more than one in five consider their own body odour to be a problem. For most, a deodorant is enough to limit the problem, but for some, not even the most efficient deodorant can control the odour. Others sweat in extreme amounts – not only from their armpits, but also from e.g. their palms or their forehead – and are soaked by their own sweat and have to change clothes several times a day. In some 3 % of the population, or almost 200,000 Danes, the problem is so serious that they are diagnosed with hyperhidrosis by their doctor, i.e. abnormally increased sweat production. These people excrete four to five times as much sweat as normally.
An average person typically excretes 0.5-2 litres of sweat during a day, but in case of hard, physical work and high temperatures, we may sweat just as much in just one hour. The American marathon runner Alberto Salazar holds the unofficial world record in sweating. As part of his preparations for the Olympic Games in Los Angeles in 1984, he exercised in a climate room to prepare for the intense heat and strong sun, which were expected on the day of the marathon. During the training sessions, scientists measured a sweat production of 3.06 l/h, and during the marathon itself, Salazar produced 5.43 kg sweat, 8.1 % of his body weight.
In people suffering from hyperhidrosis, the sweat glands excrete considerably more sweat than normally for no apparent reason. This condition can be very disturbing, as the constantly wet skin may lead to dehydration and chronic infections, and also, it may feel shameful to many people if they constantly have to wipe their palms or change shirts. The problem also has a self-reinforcing effect, as if you get stressed by sweating profusely, this will trigger nerve signals from the brain, which will make the sweat run even faster. This may cause an evil spiral, which affects your emotional life and causes social inhibition.
Scientists do not know the exact reason for the condition, which is predominant in
girls. The condition usually occurs in childhood and worsens in puberty, and it may last throughout a person's life. Some believe that a defect in the nervous system leads to overactive sweat glands, while others think that the condition is due to an imbalance in the hormone production. In 2016, Chinese scientists discovered a gene, which may be the triggering factor.
Scientists have known for a long time that hyperhidrosis is, to a certain extent, hereditary. Some 3 % of the population are suffering from this condition, but if members of your nearest family suffer from hyperhidrosis, your risk of being affected yourself increases by 50 %. Yuan-Rong Tu and his colleagues from Fujian Medical University in Fuzhou, China, suspected the gene AQP5, which creates a water channel in the membrane of the sweat-producing cells. The sweat literally flows through this channel, and the scientists’ hypothesis was that people suffering from hyperhidrosis may create more water channels than other people.
When comparing the number of water channels to the activity of the AQP5 gene in 30 people, where some were suffering from hyperhidrosis and others were healthy, the theory held water. In the profusely sweating hyperhidrosis patients, the AQP5 gene was three times as active as in the healthy people, and the patients had more than twice as many water channels in their sweat glands.
NERVE POISON GIVES DRY ARMPITS
The Chinese scientists will now examine whether a special mutation in the AQP5 gene makes the sweat-producing cells create more water channels. This knowledge may be used to develop drugs, which can reduce the activity of the gene, so that the cells will create less water channels and hopefully reduce the excretion of sweat. Doctors are already using a number of treatments, which in each their way reduce the amount of sweat. Sweaty hands and feet may e.g. be bathed in water baths with a weak electric current. According to one theory, this replaces the salt ions on the skin, electrically charged molecules, with aluminium ions,
which dampen the sweat production. The effect will last for a couple of weeks.
Another well-documented treatment is Botox injections – which are also used to smooth out wrinkles – in the palms or armpits, for example. Botox is a nerve poison, which prevents the nerve signals from the brain to activate the sweat glands. The effect lasts for up to six months. In another treatment, sweat glands in the armpits are fried lightly by sending microwaves into the skin.
SWEAT TRANSPLANT REMOVES ODOUR
Irrespective of whether you sweat profusely or just a little, you are equally subject to the other major disadvantage of sweating – the bad odour. Paradoxically, sweat in itself does not smell, and two conditions must be met to create the characteristic odour. First of all, the sweat must come from the apocrine sweat glands, which are primarily found in the armpits and crotch. They excrete a special kind of sweat, which – in addition to the normal salts also contain organic molecules like lactic acid and urea. Secondly, these substances must be broken down by bacteria and converted into foul-smelling catabolic products, before the sweat begins to smell.
The composition of the under-arm bacteria varies from person to person. Of the bacteria, which thrive in the armpits, three types in particular make the sweat smell: Staphylococcus, Corynebacterium and Anaero- coccus. Each has its own characteristic smell.
In 2013, the Belgian doctor Chris Callewaert from University of California, San Diego, USA, showed that the bacterial flora in the armpits of nine test subjects were very different. This gave him the idea for an experiment, which was published in 2016.
Callewaert used 18 pairs of close relatives, of whom one had serious problems with bad armpit smell, while the other one had a more neutral smell. He scraped off some of the bacterial flora from the nice-smelling people’s armpits and smeared the armpits of the foulsmelling relatives. A panel of odour experts with a very good sense of smell was then asked to regularly smell the test subjects’ armpits. The results were very convincing. In 16 of the 18 pairs, the relative with the stinky armpits experienced a significant improvement in his or her smell after just a few days. The effect remained for at least three months.
However, before you begin smearing yourself with another person’s sweat, it may be a good idea to put a cotton bud into your ear and see what comes out. If your earwax is hard and dry, you probably do not have to worry at all about the smell from your armpits. Then you have a version of the ABCC11 gene, which not only produces this type of earwax. It is also responsible for ensuring that the sweat from the apocrine sweat glands has a low content of the substances that transform the bacteria to stinking molecules. This genetic variant is common in the East, where problems with body odour are generally less outspoken than in the West. Here, earwax is typically soft and wet, which is connected to more sweaty armpits.
When we lie, nervousness will make us sweat more. So a lie detector measures how much the suspect sweats from his fingers.
Bacteria around a sweat pore live off nutrients in the sweat. Some types of bacteria have waste products, which smell badly.