what medical issues cause dry mouth
Saliva helps moisten and cleanse the mouth, and when the body does not product enough saliva, bad breath may result. Dry mouth may be caused by salivary gland problems, connective tissue disorders (SjÃ¶gren's syndrome), medications, or breathing through the mouth.
1 Medications: Many medications, including antihistamines and diuretics, can cause dry mouth (see above), which can cause bad breath. Other medications that may lead to bad breath may include triamterene (Dyrenium) and paraldehyde.  Morning breath: Bad breath in the morning is very common.