It’s hard to ignore your own breath when you have a mask on. Odours that you normally wouldn’t notice (hello, coffee and garlic breath) become heightened and a little too close for comfort sometimes, after lunch or a coffee break.

But even when you’re not eating or drinking, you might occasionally catch a whiff of something funky – and it might have become more noticeable since mask wearing was implemented.
You sniff again and wonder: Did you actually have bad breath or halitosis all along without realising it?

There is a chance you might be right. “When a mask covers both the nose and mouth, the concentration of any bad breath is increased, allowing us to smell it,” said Dr Edwin Chng, the medical director of Parkway Shenton. “Without the mask, even if one has bad breath, he or she may not notice it.”

There is bacteria living in your mouth all the time, said Dr Koh Chu Guan, a senior consultant with National Dental Centre Singapore's Department of Restorative Dentistry, Periodontic Unit.

"When we breathe, especially with our mouths, the moist and fetid air produced by the bacteria gets trapped in the fabric of the masks. When the droplets dry out, they leave the odour on the fabric of the masks," he said.

"The fabric probably does not matter," added Dr Koh. "If the material is thin and porous, it may trap less air and hence, the wearer may be less aware of the halitosis."

Furthermore, you could be using your mouth to breathe while wearing a mask and that might cause a drying effect. "A drier mouth, especially if you are not drinking sufficient water, may contribute to bad breath," said Dr Koh. This is worsened if you smoke or consume diuretic drinks like coffee.

To differentiate actual halitosis from mask odour, remove your mask and breathe onto your cupped hands through your mouth. The odour will not be present if it is due to the mask, said Dr Chng. Even if you’ve battled halitosis all along, wearing a mask doesn’t worsen it, he said.

Sometimes, socially awkward situations are the least of your worries when bad breath is detected. Yes, cavities, poor oral hygiene and diet (especially when you've been eating a lot of garlic, durian, dairy products and protein) can play a part.

Even talking a lot can give you bad breath as the action dries out the mouth. "Saliva has a ‘washing’ effect. People with dry mouths lose that benefit of saliva and have increased chances of having bad breath," said Dr Koh.

But sometimes, halitosis can also be a sign of more serious health issues. The medical causes can be wide ranging, said Dr Chng, encompassing gastric problems (including stomach infections and reflux disease), and cancer of the upper aerodigestive tract (such as the nasal cavity, larynx, trachea and oesophagus).

Even certain medications (such as those for treating Type 2 diabetics, aspirin, antihistamines, antidepressants, diuretics and decongestants) can be a source of your foul breath. “Certain vitamin supplements, such as omega 3 fatty acids, are also culprits,” said Dr Chng.

Here’s a look at what the various odours could possibly point to:
· Ketosis from high-protein diet: Sweet or fruity odour.
· Diabetes: Similar to the scent of nail polish remover.
· Respiratory infection: Coughs with foul-smelling mucus and breath.
· Liver or kidney issue: A musty odour, said to resemble a mix of rotten eggs and garlic, could indicate liver problems. Kidney disease may present with ammonia breath.

To keep your mouth minty fresh or at least minimise odour, see the dentist regularly to have your teeth and gums checked for periodontal disease and decay – often the root causes of bad breath, said Dr Koh.

Other than brushing, he also recommended flossing or using interdental brushes, and brushing or scraping your tongue. "The tongue is a great source of halitosis. Most of the bacteria resides on the tongue, especially further back."

What you eat plays a role, too. "Foods that have been suggested as helpful in reducing bad breath include parsley, red bell pepper and broccoli," said Dr Chng.

Dr Koh added: "Some people do find that high-carbohydrate diets, especially in snacks and sugary foods, do increase the occurrence of halitosis".

If you have to talk a lot, drink plenty of water. "If you have a dry mouth, it may be better to sip on water frequently," said Dr Koh. To mask the odour temporarily, it doesn't hurt to pop sugar-free mints or gargle with an alcohol-free mouth wash, he said.