Nonoral sources of bad breath:
· Bad breath can also be caused by systemic (medical) problems such as:
Liver problems, respiratory and sinus conditions, tonsils, kidney problems, Helibactor pylori infection, diabetes mellitus, timethylaminuria, medications, and menstruation.
· Hepatic problems:
Liver failure and cirrhosis are associated with a sulfur or “rotten egg” smell from the mouth.
Timethylaminuria, a metabolic disorder of the liver, causes the buildup of trimethylamine in exhaled air.
· Respiratory and sinus conditions:
Postnasal drip is probably the most common cause of halitosis in children. Secretions from a sinus infection, runny nose, or nasal allergy drip down the back of the throat and onto the tongue. Odor-causing bacteria thrive on these secretions, and produce volatile sulfur compounds..  These are the gases which cause bad breath.
Asthmatic children who use corticosteroids may develop bad breath due to the development of oropharyngeal candidiasis.
Enlarged adenoids may lead to mouth breathing.
Foreign bodies in the nose and respiratory tract will produce an inflammatory response, a discharge, and eventually a foul odor.
· Tonsils:
If a child’s tonsils have deep crypts, food and debris will accumulate in them, producing some bad breath. Sometimes tonsilloliths form in the crypts. These tonsilloliths are small, soft, whitish-yellow secretions which produce a foul odor as they break up.
· Kidney failure:
Kidney failure causes uremia, which produces an ammonia smell in the breath.
· Helibactor pylori infection:
This gastric infection can cause inflammatory changes in the stomach. Achalasia of the esophagus also can result in halitosis.
· Diabetes:
Uncontrolled diabetes mellitus eventually results in ketoacidosis, causing the breath to have an acetone smell.
· Medications:
Antihistamines, antipsychotics, bronchodilators, antidepressants, and antispasmodics cause dry mouth (xerostomia).
Children who have been taking antibiotics during the last month often have halitosis which is bacterial in origin. This oral malodor is transient, and usually disappears when antibiotic therapy has ceased.
· Menstruation:
Bad breath during menstruation may be caused by transient gingivitis.