It would a dentist, an ENT, an internal medicine specialist, or a hepatologist depending on what the cause of the hallitosis is due to.
Dermatologist treats that condition
The Dermatologist (skin doctor)
Foot doctor
I think its an orthapeadic doctor
See a doctor, halitosis could be a sign of acid reflux disease.
an oncologist
A psychologist.
gastroenteroligist
nuerologist
A gastroenterologist treats stomach pain.
A GP should do.
podiatrist