A foul smell from the mouth, also called bad breath, is most commonly caused by plaque and tartar buildup, gum infection, tooth decay, poor tongue cleaning, dry mouth, smoking, or food particles trapped between the teeth. In some people, throat infections, sinus problems, tonsil stones, acid reflux, diabetes, or stomach problems may also contribute to bad breath. Treatment depends on the underlying cause, but maintaining good oral hygiene is the most important step. Brush your teeth gently twice daily, clean your tongue regularly, floss between the teeth, rinse your mouth after meals, and drink enough water to prevent dryness in the mouth. An antibacterial mouthwash may help reduce bacteria and improve breath temporarily, but if tartar or gum disease is present, professional dental cleaning (scaling) is often needed for long-term relief. Avoid smoking, tobacco, and excessive sugary foods because they can worsen mouth odour. Eating fresh fruits and vegetables and maintaining good hydration may also help improve oral health. If you have gum bleeding, loose teeth, mouth ulcers, tooth pain, white patches, stomach symptoms, or bad breath that continues despite proper cleaning, it is important to consult a dentist or doctor for proper examination and treatment. Treating the root cause usually gives the best improvement in mouth odour.