General information only. This article explains dental topics in general terms and isn’t a substitute for personal advice. Everyone’s oral health and dental needs are different, so please see a dentist for advice that applies to you.
Bad breath, also called halitosis, is something most people experience at some point. Breath is often stronger first thing in the morning, after certain foods or when the mouth is dry. Ongoing bad breath, though, usually has a cause that can be found and treated.
Causes in the mouth
In most people with persistent bad breath, the cause is in the mouth. Bacteria break down food particles and proteins and release sulphur compounds with an unpleasant smell. Common sources include:
- A coated tongue. The back of the tongue has a rough surface where bacteria, food debris and dead cells collect.
- Plaque between the teeth and food trapped around crowded teeth, bridges or orthodontic appliances.
- Gum disease, where bacteria collect in pockets between the teeth and gums.
- Tooth decay and broken fillings that trap food.
- Infection around a partly erupted wisdom tooth (pericoronitis).
- Dentures that are not cleaned thoroughly or are worn overnight.
- Dry mouth, because saliva normally washes away food and bacteria. Breath is often worse when the mouth is dry, such as overnight or with some medicines.
Other causes
Less commonly, bad breath comes from outside the mouth:
- Strong foods such as garlic and onion, and alcohol.
- Smoking and other tobacco use.
- Sinus problems, post-nasal drip and tonsil stones (small, foul-smelling deposits in the tonsils).
- Gastro-oesophageal reflux.
- Fasting or very low-carbohydrate diets, which can produce a distinctive smell.
- Some medical conditions, including poorly controlled diabetes and some kidney and liver conditions.
Is it bad breath?
It is surprisingly hard to judge your own breath, because the nose gets used to familiar smells. Some people worry about bad breath that others do not notice, while others are unaware of it. A persistent bad taste in the mouth, a white or yellow coating at the back of the tongue, or bleeding gums are signs that there may be a cause worth looking into.
How bad breath is assessed
A dentist checks the teeth, gums, tongue and any dental work for sources of odour, and asks about diet, medicines, dry mouth and general health. If the mouth is healthy and the breath persists, a visit to a doctor may be recommended to look for causes elsewhere.
How bad breath is managed
Management depends on the cause. It usually involves thorough cleaning of the teeth, between the teeth and of the tongue, treating any decay, gum disease or broken fillings, and addressing a dry mouth. Mouthwashes and mints can mask odour for a short time, but they do not treat the cause.
Common questions
Does mouthwash cure bad breath?
Mouthwash can freshen breath for a short time, and some types reduce bacteria, but it does not remove the plaque, tongue coating or gum problems that are usually the source.
Can bad breath come from the stomach?
This is less common than people think. Reflux can contribute in some people, but in most cases persistent bad breath starts in the mouth. If the mouth is healthy, a doctor can look into other causes.
Why is my breath worse in the morning?
Saliva flow drops during sleep, so bacteria multiply and odours build up overnight. Morning breath is normal and usually improves after brushing, cleaning the tongue, eating breakfast and drinking water.
Can children have bad breath?
Yes. In children, common causes include a coated tongue, mouth breathing, food trapped between teeth, decay, and enlarged tonsils or a blocked nose. A small object in the nose can also cause a strong smell in young children and needs a doctor to check.
When to see a dentist
See a dentist if bad breath persists despite good cleaning, or if it comes with bleeding gums, a bad taste, loose teeth, pain or swelling. These can be signs of gum disease or infection that need treatment.