Warning of 10 potential causes of bad breath in adults

Tran Hoai Nam
21/10/2026
Hoàng Hữu Vĩ

Professional Consulting

D. Hoàng Hữu Vĩ

Dentist

Bad breath is a common health problem but is often overlooked. Although not life-threatening, bad odor from the oral cavity can seriously affect confidence in communication, personal life and work. In particular, in many cases, bad breath is a warning sign of underlying medical problems in the mouth or body. Understanding the causes, treatment, and prevention is an important step to help you effectively control this condition and improve your long-term quality of life.

 

What is bad breath?

Bad breath (scientific name is Halitosis) is a condition in which the breath emits an unpleasant odor. This odor is created by the activity of bacteria in the oral cavity, decomposing protein compounds from leftover food and dead cells and creating volatile sulfur compounds with a characteristic odor.

Anyone can experience bad breath at some point, such as bad breath in the morning after waking up due to less saliva. However, if the condition persists, it could be a sign of other underlying oral health problems or medical conditions.

Hôi miệng là tình trạng hơi thở phát ra có mùi hôi khó chịu khiến ảnh hưởng đến cuộc sống hàng ngày của mỗi người

Bad breath is a condition in which the breath emits an unpleasant odor that affects each person's daily life

 

10 causes of bad breath in adults

Poor oral hygiene

One of the leading causes of bad breath is improper oral hygiene. Not brushing your teeth thoroughly, skipping tongue cleaning, not flossing or not having your teeth cleaned regularly causes leftover food and bacteria to accumulate in the oral cavity. 

These bacteria decompose organic matter, releasing sulfur compounds that cause odors. This is the most common cause but is easily subjective.

Gingivitis and periodontitis

Gum diseases such as gingivitis and periodontitistThe disease progresses silently and is difficult to detect in the early stages. As the disease progresses, periodontal pockets form around the roots of the teeth, where odor-causing bacteria accumulate. 

These bacteria not only create an unpleasant odor but also destroy the tooth support structure, leading to receding gums, loosening and tooth loss if not treated early.

Tooth decay

Caries, especially cavities deep inside the jaw or in large molars,can easily become a place for food and bacteria to accumulate. When not filled or treated promptly, progressive tooth decay will cause pulp inflammation and pulp tissue necrosis, creating conditions for bacteria to thrive and cause persistent bad breath.

Dry mouth (reduced salivation)

Saliva has the role of neutralizing acids, washing away food residue and inhibiting the growth of bacteria. When you have a dry mouth – due to drinking less water, medication side effects, age, or certain salivary gland diseases – the mouth's self-cleaning mechanism is impaired. 

As a result, bacteria thrive and cause a characteristic odor. This is a common cause in the elderly and people with chronic diseases.

Pharyngitis, tonsillitis

Chronic tonsillitis or pharyngitis causes the tissues in the throat area to continuously become inflamed, secreting mucus, creating conditions for bacteria to multiply. Some people may have tonsil nodules – small white, strong-smelling masses located in the tonsil cavity. When pushed out, they can create a very unpleasant odor, causing bad breath despite thorough oral hygiene.

Gastroesophageal reflux

Breath that smells sour, rotten eggs or acid is often a sign of gastric reflux disease. When stomach acid flows up into the esophagus, sulfur compounds and gases from the stomach can be pushed back up into the oral cavity.

In addition, Helicobacter pylori bacteria are also thought to be linked to chronic bad breath in some people.

Smoking and drinking alcohol

Smoking habits not only cause unpleasant odors in the mouth but also dry the mouth, damage gum tissue and reduce the self-cleaning ability of saliva. Besides, alcohol in alcohol can also change the pH of the oral cavity and increase the growth of bacteria that cause bad breath. 

People who smoke and drink alcohol regularly have a much higher rate of bad breath than normal people.

Foods with strong odors

Foods such as onions, garlic, dried fish, fish sauce, curry... after digestion, will release volatile compounds through the lungs, leading to a characteristic breath odor. This odor can last from a few hours to a whole day if you do not clean your teeth thoroughly. 

In particular, people with a diet low in green vegetables and fruits are more susceptible to bad breath due to the lack of enzymes that support digestion and natural cleaning.

Unclean prosthetics

Removable dentures, porcelain bridges, and braces, if not cleaned properly, will become a haven for plaque and bacteria. In particular, food that is often stuck between teeth and braces without being thoroughly cleaned will quickly ferment, creating a bad odor. 

This happens quite commonly in older people or people with braces who do not receive proper hygiene instructions.

Systemic diseases

Some systemic diseases such as diabetes, liver failure, kidney failure can affect the odor in the breath. 

For example, people with kidney failure often have the smell of ammonia on their breath, and people with poorly controlled diabetes may have acetone-smelling breath. These are signs that need to be paid attention to in order to promptly detect the disease through a general examination.

Các nguyên nhân gây hôi miệng phổ biến ở người lớn

Common causes of bad breath in adults

 

Effective ways to treat bad breath

To treat bad breath, it is necessary to determine the correct cause and have appropriate treatment methods. You can start with simple home remedies, combined with medical treatment when necessary.

Thorough oral hygiene

Brush your teeth at least 2–3 times a day with fluoride toothpaste. Use dental floss or a water flosser to clean between teeth - where bacteria can easily live. Don't forget to clean your tongue, because this is where many odor-causing bacteria accumulate. In addition, you should rinse your mouth with salt water or antiseptic mouthwash every day to increase cleaning effectiveness.

Treatment of dental diseases

If you have tooth decay, gingivitis, periodontitis... you need to go to the dentist for complete treatment. Filling cavities, removing tartar, cleaning gum pockets or extracting severely damaged teeth are necessary steps to eliminate odor-causing bacteria.

Special examination of ear - nose - throat specialist

Bad breath accompanied by a sore throat, tonsillitis or tonsil stones can be a sign of throat disease. Need to be examined and treated by the right specialist. You can use medicine or tonsillectomy if necessary. Cleaning the throat with physiological saline also helps significantly reduce odor.

Check the digestive system

If the breath has a sour or bitter odor, it may be related to gastric reflux or ulcers. Patients should have an endoscopy, test for H.pylori bacteria and receive treatment according to the instructions of a gastroenterologist to completely control this condition.

Control of systemic diseases

Diabetes, liver failure, kidney failure can all cause a characteristic bad odor in the breath. Treating these diseases not only improves overall health but also helps overcome persistent bad breath.

Eliminate habits that cause odor

Smoking cigarettes and drinking alcohol regularly cause the oral mucosa to become dry and damaged, easily creating conditions for bacteria to grow. Quitting smoking and limiting alcohol is necessary if you want to thoroughly treat bad breath.

Cleaning dental instruments

People wearing removable dentures need to soak and clean their dentures every day. For people with braces, it is necessary to use interdental brushes, water flossers and specialized tools to thoroughly clean the braces - places where food can easily stick and cause odors.

 

How to prevent bad breath in the long term

Prevention is the most effective way to keep breath fresh and limit the risk of recurrence. The habits below will help you maintain stable oral health every day.

Maintain oral hygiene every day

Brush your teeth after eating and before bed to prevent plaque buildup. Use dental floss instead of toothpicks, clean your tongue, and rinse your mouth regularly to remove odor-causing bacteria. You should drink water regularly to keep your mouth moist and avoid dry mouth - a common cause of bad breath.

Regular dental check-ups

Visit the dentist every 6 months to help detect early tooth decay, gingivitis, plaque or other unusual signs. Regular dental scaling also helps eliminate sources of unpleasant odors that you cannot clean at home.

Maintain a healthy diet

Eat lots of green vegetables and fruits to help increase salivation - the mouth's natural self-cleaning mechanism. Limit sweets, foods high in starch, fat, and strong-smelling foods such as garlic and fish sauce if you cannot rinse your mouth immediately afterward.

Limit tobacco and alcohol

Not smoking is a prerequisite to keep your oral cavity healthy. Alcohol also needs to be limited because it can dry the mouth and affect tooth enamel, thereby creating conditions for bacteria to thrive.

Monitor general health

Bad breath is sometimes a sign of an underlying disease. Therefore, do not be subjective when bad breath persists despite taking good care of your mouth. Regular examinations help to screen for internal diseases early and support timely treatment if problems arise. If you are getting a dental implant you should also monitor and have regular check-ups!

Các cách phòng ngừa hôi miệng hiệu quả

Effective ways to prevent bad breath

 

To get detailed examination and advice on your dental condition, as well as detect and treat bad breath, make an appointment with the team of experienced experts at Lac Viet Intech Dental today! 

 

  • Hotline:0866.38.0033 (or 1900.6421)

 

Lac Viet Intech Dental branch system:

 

  • TP. HCM:No. 90 - 92 Ngo Gia Tu, Ward 9, District 10, City. HCM
  • Hanoi:
  • No. 91 Hue Street, Hai Ba Trung, Hanoi
  • No. 168 Lang Street, Dong Da District, Hanoi
  • No. 426 Minh Khai, Hai Ba Trung District, Hanoi
  • No. 27 Nguyen Van Huyen, Cau Giay District, Hanoi
  • Nghe An:No. 24 Cao Thang, Hong Son Ward, Vinh City, Nghe An
  • Hai Phong:107 To Hieu, Le Chan, Hai Phong City

 

 

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