Thumb-sized device quickly ‘sniffs’ bad breath

In case you forget the mints on a first date, scientists have created a thumb-sized portable prototype device that quickly ‘sniffs’ bad breath.

Created by experts in South Korea, the device detects the presence of hydrogen sulfide (H2S) – the gas that makes breath bad.

After exhalation into the device, the presence of H2S on the breath could be displayed on a companion smartphone app.

In addition to being a social misstep, bad breath is a natural warning sign that may indicate serious dental problems.

Image from the Korean experts’ paper shows how the device can provide rapid detection of hydrogen sulfide in human breath

The research was conducted by experts from Samsung Electronics and 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 write in their paper.

‘This research offers possibilities for direct, very reliable and rapid detection of H2S in real human breath without the need for collection or filtering equipment.’

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

H2S and other smelly sulfur byproducts are excreted as waste by bacteria on the tongue and below the gumline.

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


Contrary to popular belief, you cannot control your breath by blowing your hand. According to dentist and bacteriologist Dr. Howard Katz, founder of The Breath Company, it just doesn’t work.

Your body is designed in such a way that you cannot perceive your own smell and your senses get used to the smell of your own breath.

It’s a process called acclimation that we’ve developed over centuries of evolution – it helps us distinguish strange smells quickly without being overwhelmed by our own smells.

You constantly exhale your own breath, so you get used to your own smell.

Previously, some devices were able to measure small amounts of H2S, but they require exhaled air to be collected and tested on expensive instruments in a lab, which is not feasible 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 combined with noble metal catalysts, they can become more sensitive and selective.

To develop a small real-time bad breath analyzer, 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 the tungsten into its metal oxide form.

Electrospinning is a method of producing ultra-fine fibers as small as a billionth of a meter in diameter (a 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 decrease in electrical resistance in less than 30 seconds.

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

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

In addition to being a social misstep, bad breath is a natural warning sign that may indicate serious dental problems

In addition to being a social misstep, bad breath is a natural warning sign that may indicate serious dental problems

Finally, the team coated interdigital gold electrodes with the nanofibers and combined the gas sensor with humidity, temperature and pressure sensors in their small prototype.

The device correctly identified bad breath 86 percent of the time when people’s breath was breathed directly onto it.

Although the device has yet to be marketed, it can be built into very small devices such as key fobs for quick and easy self-diagnosis of bad breath.

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


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 teeth — and on your tongue and gums can produce unpleasant-smelling gases. These bacteria are also responsible for gum disease and tooth decay.

Food and drink

Eating highly flavored foods, such as garlic, onions, and herbs, is likely to make your breath smell. Strong-smelling drinks, such as coffee and alcohol, can also cause bad breath.

Bad breath caused by food and drink is usually temporary. Good oral hygiene also helps.

To smoke

Smoking not only makes your breath smell, but it also stains your teeth, irritates your gums and reduces your sense of taste.

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

Crash diets

Crash diets, fasting and low-carb diets are another possible cause of bad breath. They cause the body to break down fat, which produces chemicals called ketones, which you can smell when you breathe.


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

If the medication you are taking is causing bad breath, your doctor may be able to recommend an alternative.

Medical conditions

In rare cases, bad breath can be caused by certain medical conditions. Dry mouth (xerostomia) can affect the flow and composition of saliva.

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

In some cases, gastrointestinal disorders can also cause bad breath. For example, a bacterial infection of the gastric mucosa 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, for example, bronchiectasis, bronchitis, tonsillitis, and sinusitis.


Some people are convinced that they have bad breath when they don’t. This psychological condition is called halitophobia.

Source: NHS Choices