What Causes Bad Breath?

Where Bad Breath Starts

The medical term is halitosis, and in the great majority of people it begins inside the mouth. Bacteria feed on scraps of food and shed cells, and as they digest them they release volatile sulphur compounds, the gases behind that familiar smell. They gather wherever cleaning falls short: in the grooves at the back of the tongue, in the narrow contacts between molars, under the edge of a cracked filling, and in the pockets that open up when gums are inflamed.

Saliva is the mouth's natural rinse, and when it slows down the bacteria get the upper hand. That's why breath is at its worst when you wake, after a long-haul flight, or on a day you've barely drunk anything. Breathing through your mouth and a number of everyday medicines dry things out further. Because the cause is physical, so is the cure: clear the deposits away and the odour leaves with them.

The Usual Culprits

• A coated tongue, particularly the film right at the back that a toothbrush tends to skip
• Plaque in the gaps between teeth, out of a brush's reach
• Gum disease, anywhere from mild inflammation to deep pockets harbouring bacteria under the gum
• Dryness, typically first thing, from mouth breathing or as a side effect of medication
• Smoking, which leaves its own odour and raises the risk of gum disease
• Pungent food like garlic, onions and strong spices, which can hang around for a day
• A cavity or broken filling where food collects and decays
• Dentures, retainers or aligners that miss their daily clean
• Very low-carbohydrate diets and long fasts, which can make breath smell sharp, almost like nail varnish

A Daily Routine That Fixes Most Cases

• Brush for two minutes, morning and night, with fluoride toothpaste, tilting the brush so the bristles reach where gum meets tooth
• Clean every gap between your teeth once a day, with interdental brushes, or floss if the spaces are very tight. Most people leave this out, and it has the largest effect on breath
• Clean your tongue from back to front. A scraper shifts the coating at the back far better than a brush does
• After brushing, spit out the excess without rinsing, so the fluoride stays on your teeth
• Keep a water bottle with you, and if your mouth runs dry, chew sugar-free gum after eating
• Eat breakfast. Chewing restarts saliva flow and clears overnight odour
• Give dentures, retainers and aligners a daily clean, and leave dentures out while you sleep
• If you smoke, giving up does more for your breath and gums than anything else here
• Keep your hygiene appointments, so tartar and stain don't build up into new hiding places for bacteria

Stick with it for two to three weeks. If nothing has changed by then, the source is probably somewhere you can't reach yourself.

Could It Be Gum Disease?

When bad breath refuses to go, gum disease is what we most often find. Plaque left at the gum margin calcifies into tartar, the gum becomes inflamed and starts to separate from the tooth, and the gap that forms is an ideal home for odour-producing bacteria. Watch for bleeding when you brush or floss, red or swollen gum edges, gums that seem to have receded, and an unpleasant taste that returns shortly after you've brushed.

In its early form, gingivitis, gum disease usually settles with a professional clean and a better routine at home. Once it has progressed to periodontitis, it needs deep cleaning beneath the gum, carried out in stages at £100 each.² Our gum disease guide covers the symptoms and treatment in more depth.

How a Hygiene Appointment Helps

Appointments with Stefanie Goodall, our dental hygienist, can be booked directly, without seeing a dentist first. A Classic Smile Clean usually takes 30 minutes. Stefanie checks and measures your gums for early signs of disease, removes tartar from above and just under the gum line, and clears plaque and staining. A Diamond Smile Clean adds Airflow, which blasts a fine mix of warm water, air and powder into the awkward spots around implants, bridges and braces. Before you leave, she shows you exactly where bacteria are collecting in your mouth and which brushes will reach them.

A Classic Smile Clean is £99 and a Diamond Smile Clean with Airflow is £134; where there's a lot of build-up, a longer 60-minute deep clean costs £165.² Hygiene visits are also part of our dental plans. For most people with stubborn bad breath, one appointment and an improved home routine sort it out.

Dry Mouth, and Cleaning What You Wear

Dryness is one of the causes people least expect. Saliva flushes bacteria away and buffers the acid they produce, so when it's in short supply, breath deteriorates quickly. Typical reasons are sleeping with your mouth open, certain medicines for blood pressure, hay fever, low mood and an overactive bladder, and not drinking enough through the day. Regular sips of water, sugar-free gum and switching to an alcohol-free mouthwash all help. If the dryness never lets up, mention it to your GP, because a different medicine can sometimes solve it.

Dentures, retainers and Invisalign aligners collect plaque just as teeth do. Clean them daily using a soft brush and a cleaner designed for them, keep them away from hot water, and take dentures out at night so the gums underneath can recover. Anything that spends hours in your mouth needs cleaning as carefully as your teeth.

When the Cause Lies Elsewhere

Now and then the smell comes from beyond the mouth. Possible sources include sinusitis, mucus dripping down the back of the throat, tonsil stones, reflux and certain stomach conditions, and a sweet, pear-drop smell can point to diabetes that isn't well controlled. The giveaway is a clean, healthy mouth with breath that stays the same regardless, or that worsens when you have a cold or a bout of heartburn. If we've examined your teeth and gums and found them healthy, see your GP and mention that your mouth has already been checked, so they can concentrate on other causes.

Questions

This guide explains the options in general terms. Only an examination can tell you which of them suits your own teeth.