Breath isn’t always minty fresh, for example, in the morning, or when hungry or dieting, or after eating foods with a strong odour, such as garlic or onions.

Experts say there are various causes of bad breath, for example, decreased saliva. Saliva has a cleaning action that helps reduce or eliminate bad breath. When saliva decreases, bacteria can grow, causing bad breath. And it is important to understand the reason behind it so as to find a way to get rid of it.

Gonzalue Niyigaba, a dentist at University Teaching Hospital of Kigali (CHUK), says bad breath at times can be a sign of gum disease. But, he says, the most common cause of bad breath or halitosis is poor oral hygiene, and this could be due to not brushing adequately, or at all.

The medic goes on to explain that when one does not clean the teeth and oral cavity regularly, residual food particles tend to stay around teeth and gums. Bacteria gather over these particles and proliferate causing plaques.

Also, sugary, sticky food items like cakes, candy, chocolate, are more implicated in causing mouth infections.  

He says all these result in dental and or gum infection, which manifests as toothache, swelling, and pain around gums, with or without bleeding.

Dr Rachna Pande, a specialist in internal medicine, says another reason as to why one may experience a foul smell from the mouth is brushing the teeth with an old toothbrush.

According to her, this is not a good idea, because as the bristles of an old toothbrush become worn out, it does not clean the teeth adequately.

On the other hand, she says, a toothbrush with hard bristles can injure the gums causing abrasions, which can be a focus for infection. 

In addition to this, Dr Pande says, it’s important to understand that repeated or persistent infection tends to weaken the dental roots resulting in tooth or teeth fall; therefore, it is important to maintain good oral hygiene.

"Ideally, one should brush teeth after every meal. If it’s difficult, it should be done at least twice every day, once in the morning after waking up and another time after dinner before sleeping,” she advises.

Also, Dr Pande notes that in between, after eating anything, the mouth can be rinsed with clean water.

"Rinsing the mouth with diluted antiseptic mouth wash or with lukewarm saltwater is also useful to prevent infections and resultant bad breath,” she adds.

Jean Claude Nkusi, a dentist in Kigali, says when using a toothbrush, one should ensure that it’s with soft bristles which are in good condition, and it should be moved over the entire set of teeth. 

He points out that there is also a need for flossing and if not daily, one should do it at least two to three times every week. The tongue should also be cleaned regularly. 

Nkusi mentions that some foods like raw onions, garlic, spices, also cause bad breath after consumption. Also, use of tobacco, either by smoking or consuming orally, causes bad breath.

Some medicines like those used to treat allergy, antidepressants, the ones used to remove excess water from the body, are known to cause bad breath as an adverse effect.

Dr Pande says it’s ideal to understand that some infections of the mouth like protozoal, viral infections cause bad breath as one of the manifestations. But here, along with bad breath, she says, there is associated pain and or swelling.

She goes on to note that any one of these infections, if present, can be diagnosed easily and is curable by suitable antimicrobial drugs.

On top of this, infections of the nose, throat, sometimes ear, or even lung infections may cause bad breath. Chronic infections of the air sinuses in skull have also been identified as a cause for bad breath. Treatment of the underlying infection cures halitosis as well.

"Bad breath may be due to allergic rhinitis, where one has repeated or persistent running of the nose or nasal congestion due to allergy to something used or prevalent in the atmosphere. Regular steam inhalation can help prevent it,” she says. 

According to Dr Rachna, a benign or malignant tumour in the nose or mouth, or malignant ulcer, may result in bad breath. But here along with halitosis, there would be other associated symptoms like pain, weight loss, and weakness.