If you avoid pungent foods and take care of your oral hygiene, but still have bad breath, there is a possibility that you usually remain stressed.
When we're stressed, our sympathetic nervous system kicks in. And one consequence of that is that it cuts the production of saliva.
As a result, the mouth becomes dry. Anything that dries the mouth makes bad breath worse.
The gases released by bacteria are usually contained by saliva and swallowed. But if you have a dry mouth -- known as xerostomia -- the saliva evaporates so the gases are released.
Furthermore, the bacteria can stick to the mouth more, making things worse.
There are particular types of bacteria found on the tongue that can also contribute to bad breath.
You may assume a mouthwash will freshen breath, but some that contain alcohol can actually do the reverse.
Sleeping with your mouth open, smoking, drinking coffee and exercising without hydrating properly also dry out the mouth.
Sjogren's syndrome, an auto-immune condition where the body attacks the tear and salivary glands, reducing the production of fluid, can also lead to bad breath brought on by a dry mouth.
Another cause of bad breath is salivary stones blocking the salivary glands.
These form when food debris reacts with chemicals in the saliva. This crystallises into a stone that can block the salivary ducts, stopping saliva flow and causing dryness and bad breath.
Bad breath may also occur if you stick to a low-carb diet.
In the absence of carbohydrates for energy, the liver breaks down fat instead. This produces chemicals called ketones, which have a distinct metallic smell.
This can also happen in people with uncontrolled diabetes because the liver can't break down sugar, so breaks down fat instead.