Bad Breath (Halitosis): What Causes It and How to Fix It

At Gartside Street Dental Lounge in Manchester city centre, our clinicians share practical guidance to help you make confident treatment decisions.

Bad breath, or halitosis, is one of those conditions that almost no one talks about and almost everyone worries about at some point. One of the cruel facts about it is that most people cannot reliably smell their own breath: the olfactory system adapts to constant smells within a few seconds, and the cup-the-hands-and-breathe test does not work because exhaled breath bypasses the nose. As a result, most people first learn about a bad breath issue from a partner, friend, or close colleague, often years after it started. This post explains what actually causes bad breath, why mouthwash usually fails as a fix, and what works.

The first piece of reassurance is that bad breath is almost always treatable, and almost never a sign of severe systemic disease. Roughly 80 to 90 per cent of cases originate within the mouth itself. The remaining 10 to 20 per cent come from sinus or throat conditions, dietary causes, reflux, and rarely systemic disease such as poorly controlled diabetes or kidney disease. The mouth-based causes are by far the most common, and almost all of them respond to straightforward intervention.

The single biggest source of bad breath in most adults is the tongue, specifically the back two-thirds of it. The tongue surface is heavily ridged, and the back part is rarely touched by toothbrushing or eating. Bacteria accumulate in those ridges and produce volatile sulphur compounds — the chemical class responsible for most bad breath odours. Most people brush their teeth thoroughly twice a day and ignore their tongue entirely. Tongue cleaning, done properly, often resolves a meaningful portion of cases on its own.

The second major source is gum disease, particularly the early-to-moderate stages of gingivitis and periodontitis. Bacteria in inflamed gum pockets release volatile sulphur compounds steadily, regardless of brushing. If your bad breath is accompanied by bleeding gums, gum disease is almost certainly part of the picture, and treating one usually improves the other.

The third source is dry mouth. Saliva is your mouth’s natural cleansing system: it dilutes bacteria, washes away food debris, and contains antimicrobial proteins. When saliva flow is reduced, bacterial activity increases. Common causes of dry mouth include dehydration, mouth breathing (especially at night, which is why morning breath is universal), medications such as antihistamines, antidepressants, blood pressure medications and antimuscarinics, age, and a range of medical conditions. If you wake up regularly with severely bad breath, mouth breathing during sleep is a likely contributor.

The fourth source is food and drink. Garlic and onion compounds in particular are absorbed through the gut and exhaled by the lungs for hours after a meal — they are not just a mouth-surface issue. Coffee, alcohol, and smoking all contribute, both directly and by drying the mouth. These causes are usually transient and easy to manage by adjusting what you consume before social situations.

The fifth set of causes lies beyond the mouth. Postnasal drip from chronic sinus problems, tonsil stones (small whitish concretions that collect in the crypts of the tonsils and have a distinctive sulphur smell when crushed), and pharyngeal infections can all produce bad breath that originates above or behind the mouth. If your dentist has cleared the dental causes and the breath issue persists, an ENT or GP referral is the next step.

A sixth source is gastric reflux. Gastro-oesophageal reflux disease (GORD) can produce sour breath, particularly in the morning or when you have been lying down. It is often missed in the bad-breath conversation because the symptoms can be subtle. If you also experience heartburn, regurgitation, or chronic throat clearing, reflux is worth investigating with a GP.

Why does mouthwash so often fail to fix the problem? Because mouthwash masks rather than treats. The bacteria producing volatile sulphur compounds are embedded in biofilm on the tongue, between teeth, and in gum pockets — places that mouthwash simply does not reach in meaningful concentration. Antibacterial mouthwashes such as those containing chlorhexidine can help in the short term as part of treating gum disease, but they are not a long-term solution and prolonged daily use can cause staining and taste changes. A pleasant smell after rinsing is not the same as treating the cause.

What actually works, in order of impact for most adults: a dedicated tongue scraper, used once a day, gently from back to front, four or five passes. This is the single highest-leverage intervention and costs a few pounds. Daily interdental cleaning with brushes or floss to disrupt biofilm between teeth. Treating any underlying gum inflammation through professional cleaning. Staying genuinely hydrated by sipping water throughout the day rather than drinking only at meals. Sugar-free chewing gum after meals to stimulate saliva. Reducing coffee and alcohol where possible. Addressing mouth breathing if it is a factor — sometimes a GP can help with the underlying cause, such as nasal congestion.

When dry mouth is a significant contributor and lifestyle changes are not enough, prescription products help. Artificial saliva sprays, gels, and lozenges are available, and your dentist can recommend the right format. A full medication review with your GP can also be useful — sometimes there is an alternative to the drug that is drying you out.

When should you escalate from home care to a dental visit? If you have been doing tongue scraping, interdental cleaning, and the basics for two to three weeks without improvement, it is time to be assessed. Your dentist will look for hidden cavities, leaking fillings, periodontal pockets, and other dental sources you might not have noticed yourself. We can also identify whether the issue is more likely beyond the mouth and signpost an appropriate next step.