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Thumb size device “quickly” sniffs out “bad breath

In case you forget the coins on a first date, researchers have made a portable prototype device that is the size of a thumb that quickly “sniffs out” bad breath.

The device is made by experts in South Korea and detects the presence of hydrogen sulfide (H2S) – the gas that makes breathing difficult.

After exhaling in the device, the presence of H2S on the breath can be displayed in an included smartphone app.

In addition to a social faux pas, bad breath is a natural warning sign, potentially indicating serious dental problems.

The photo from the Korean experts' paper shows how the device can offer rapid detection of hydrogen sulfide in human breath

The photo from the Korean experts’ paper shows how the device can offer rapid detection of hydrogen sulfide in human breath

The study was conducted by experts at Samsung Electronics and the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, South Korea.

Continuous monitoring of hydrogen sulfide (H2S) in human breath for early diagnosis of halitosis [bad breath] is of great importance for the prevention of dental diseases, they say in the newspaper.

‘This study provides opportunities for direct, highly reliable and rapid detection of H2S in true human respiration without the need for collection or filtration equipment.’

H2S is created in the body in small doses – and is perhaps best known for carrying the dry smell of rotten eggs.

H2S and other foul-smelling sulfur by-products are excreted as waste by bacteria on the tongue and below the gum line.

Unfortunately for the people around us, they are present in the air we exhale, which makes good oral hygiene crucial on a first date or a job interview to combat the odor.


Contrary to many people’s beliefs, you can not check your breathing by blowing into your hand. It simply does not work, according to dentist and bacteriologist Dr. Howard Katz, founder of The Breath Company.

Your body is designed so that you can not detect your own smell and your senses get used to the smell of your own breath.

It is a process called acclimatization that we have developed over centuries of evolution – it helps us to be able to distinguish strange smells quickly without being overwhelmed by our own smell.

You breathe out all the time, so you get used to your own smell.

In the past, some devices have been able to measure small amounts of H2S, but they require exhaled air to be collected and tested on expensive instruments in a laboratory, which is not possible for consumers.

Previous studies have shown that when some metal oxides react with sulfur-containing gases, their electrical conductivity changes.

And when metal oxides are paired with precious metal catalysts, they can become more sensitive and selective.

So in order to develop a small, bad breath analyzer in real time, the team wanted to find the right combination of substances that would elicit the fastest and strongest response to H2S in air blown directly onto it.

The researchers mixed sodium chloride (an alkali metal salt) and platinum (a noble metal catalyst) nanoparticles with tungsten.

They then electrospun the solution into nanofibers which they heated, converting tungsten to its metal oxide form.

Electrospinning is a method of producing ultrafine fibers that measure as small as one billionth of a meter in diameter (one nanometer).

In preliminary tests, the composite made of equal parts of each metal had the greatest reactivity to hydrogen sulfide, which the team measured as a large reduction in electrical resistance in less than 30 seconds.

Although this nanofiber reacted with a few sulfur-containing gases, it was most sensitive to H2S.

It created a response 9.5 and 2.7 times larger than with dimethyl sulfide or methyl mercaptan, respectively, which also contain sulfur.

In addition to a social faux pas, bad breath is a natural warning sign, potentially indicating serious dental problems.

In addition to a social faux pas, bad breath is a natural warning sign, potentially indicating serious dental problems.

Finally, the team coated interdigitated gold electrodes with the nanofibers and combined the gas sensor with humidity, temperature and pressure sensors for its small prototype.

The device correctly identified bad breath 86 percent of the time when the breath of humans was exhaled directly on it.

Although the device is not yet commercialized, it can be incorporated into very small devices such as keychains for quick and easy self-diagnosis of bad breath.

The system is described in more detail in the team’s paper, published in the journal ACS Nano.

Causes of bad breath (HALITOSE)

There are a number of possible causes of halitosis:

Poor oral hygiene

This is the most common cause. Bacteria that build up on your teeth – especially between them – as well as the tongue and gums, can produce unpleasant-smelling gases. These bacteria are also responsible for gum disease and tooth decay.

Food and drink

Eating foods with strong flavors, such as garlic, onions and spices, are likely to make your breath smell. Strong-smelling beverages, such as coffee and alcohol, can also cause bad breath.

Bad breath caused by food and drink is usually temporary. Good dental hygiene will also help.


In addition to making the breath smell, it stains the teeth, irritates the gums and reduces the sense of taste.

It can also significantly affect the development of gum disease, another important cause of bad breath.

Crash diet

Crash diets, fasting and low-carbohydrate diets are another possible cause of bad breath. They cause the body to break down fats, which produce chemicals called ketones that can be smelled on the breath.


These include: nitrates – these are sometimes used to treat angina; some chemotherapy drugs; and sedatives (phenothiazines).

If the medicine you are taking is causing bad breath, your GP may recommend an alternative.

Medical condition

In rare cases, bad breath can be caused by certain medical conditions. In dry mouth (xerostomy) the saliva flow and composition can be affected.

Dry mouth can sometimes be caused by a problem in the salivary glands or by breathing through the mouth instead of the nose.

In some cases, gastrointestinal conditions can also cause bad breath. For example, a bacterial infection of the stomach and small intestine (H. pylori infection) and gastroesophageal reflux disease (GORD) have been linked to bad breath.

Other medical conditions that can cause bad breath include diabetes and lung, throat or nose infections – such as bronchiectasis, bronchitis, tonsillitis and sinusitis.


Some people are convinced that they have bad breath when they do not. This psychological condition is called halitophobia.

Source: NHS Choices

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