The possible causes are as follows.
Chronic pharyngitis can cause dry heaving due to irritation of the pharynx by the smell of toothbrush or toothpaste.
Patients with oral diseases such as gingivitis, pericoronitis and calculus can also suffer from varying degrees of dry heaving caused by incorrect brushing.
When people with poor gastrointestinal function or a heavy pregnancy reaction brush their teeth, causing a conditioned reflex that can produce symptoms of dry heaving.