a man suffering with acid reflux.

Can bad breath come from the stomach?

If you suffer from bad breath (halitosis) and are looking for ways to eliminate it for good, it’s important you look to address all possible causes. While causes such as poor dental hygiene, smoking, recently consumed food, and the use of certain medications are often the first you consider, did you know the issue could in fact be stemming from your stomach? 

Bad breath caused by a stomach issue can be tricky to identify and difficult to treat just with brushing and flossing alone. With this in mind, it’s important to be aware of all the signs and signals that can help you decipher between harmless bad breath caused by a particularly garlicky meal and halitosis that is symptomatic of a more serious stomach condition.[1] 

In this blog post, we discuss what can cause bad breath from the stomach, look into whether or not fasting leads to bad breath in this way, and explain some of the potential cures.

What causes bad breath from the stomach?

Issues with your digestive tract and stomach more generally can cause a whole host of seemingly random symptoms, including bad breath. For this reason, if you have ruled out the more common causes of bad breath but are still experiencing it, it might be time to determine what stomach issue you could be suffering from. While this process should always start with a trip to your GP to discuss your symptoms, below are some of the most common causes of bad breath from the stomach.

  • GERD (chronic acid reflux) 

Gastroesophageal Reflux Disease (GERD) is a common condition that impacts the ring of muscle located between your esophagus and your stomach. When you suffer from GERD, excess acid produced by your digestive tract travels back up into the oesophagus causing heartburn. This can also cause a sour taste in your mouth, leading to bad breath.[2] 

  • Stomach ulcers

It is thought that there is a link between H. pylori bacteria, that causes stomach ulcers, and bad breath. A recent study published in the journal, Medical Principles and Practice actually found that patients with halitosis and H. pylori present in the stomach saw their bad breath improve when their H. pylori infections were treated with antibiotics.[3] 

  • Kidney disease

One of the first symptoms of chronic kidney disease, bad breath is caused by an excess of urea in the bloodstream that has not been filtered out by the kidneys. This typically presents itself with a foul-smelling fishy odour.[4] 

  • Bowel obstruction

When broken down food cannot move down the intestinal tract, the entire contents of your digestive tract starts to ferment, producing a bad smell. One way this foul odour can escape the body is through the mouth.[5] 

Can fasting cause bad breath?

To put it simply, yes – fasting can cause bad breath. However, this typically has nothing to do with your stomach. When fasting, the production of saliva in your mouth reduces. As saliva provides us with protection against the oral bacteria that can cause bad breath, a reduction in this bodily fluid naturally sees a build up of this bacteria in your mouth, and an increased possibility of bad breath. Fortunately, once a fast is broken and regular eating habits have resumed, the production of saliva in your mouth should return to normal, helping to fight bad breath.[6] 

How to cure bad breath coming from the stomach 

The only way to ‘cure’ bad breath caused by the stomach is to identify and treat the root cause. For this reason, if you suspect your halitosis is being caused by a stomach condition, it is important that you talk to your doctor. They will discuss all of your symptoms with you, attempt a diagnosis and then help to develop a personal treatment plan showing you how to eliminate bad breath from the stomach.[1]

Additionally, there are also a number of day-to-day changes you can make to your life to help freshen up your breath. These include:[1] 

  1. Avoiding triggers – try to note the food and drink that seem to make your bad breath worse. These may include things like dairy, spicy foods and citrus. Additionally, trying to avoid triggers such as stress or overexertion can also help.
  2. Keeping on top of your oral hygiene – ensure you always brush your teeth twice each day and continue to use floss and mouthwash to remove any odour-causing food particles and bacteria. Using a tongue cleaner every day can also aid this process.
  3. Taking a probiotic – if bad breath can be caused by a stomach issue, it follows that a healthier gut could lead to a better smelling breath. With this in mind, talk to your GP about taking a daily probiotic or simply add a portion of natural yoghurt to your day-to-day diet.


[1] https://www.nhs.uk/conditions/bad-breath/

[2] https://www.nhs.uk/conditions/heartburn-and-acid-reflux/

[3] Katsinelos P et al. Eradication  Therapy in Helicobacter pylori-Positive Patients with Halitosis:  Long-Term Outcome. Med Princ Pract. 2007;16:119-123.  Doi:10.1159/000098364. Available at: https://karger.com/mpp/article-abstract/16/2/119/204189/Eradication-Therapy-in-Helicobacter-pylori?redirectedFrom=fulltext

[4] Santaella, Natalia-Garcia et al. “Halitosis, reduced salivary flow and the quality of life in pre-kidney transplantation patients.” Journal of clinical and experimental dentistry vol. 12,11 e1045-e1049. 1 Nov. 2020, doi:10.4317/jced.57282 Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680576/

[5] Tungare S, Zafar N, Paranjpe AG. Halitosis. [Updated 2023 Aug 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534859/

[6] https://www.nhs.uk/conditions/dry-mouth/

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