The senses of taste and smell are as closely associated in pathological states as they are in the normal state. Therefore hallucinations of these senses are usually considered together.
Their clinical significance varies, depending upon whether they coexist with psychic and somatic disorders of an acute nature, or whether they appear in the course of a chronic psychosis.
In the first case they often result from dryness and inflammation of the nasal and buccal mucous membranes or glands. They disappear with the disturbances of these glands, and they may be modified very favorably by appropriate treatment. Their importance with regard to prognosis in such cases is very slight.
It is altogether different in the second case, when they supervene independently of the above causes in the course of chronic psychoses. They almost always indicate a profound alteration of personality and progress toward dementia.
Hallucinations of taste and smell are mostly unpleasant. The patients complain of nauseating odors; putrid emanations are blown toward them; they are made to eat fecal matter; poisons are poured into their mouth, etc. They make use of certain means of defense, such as spitting, stuffing the nostrils with cotton or paper, and, what constitutes a very grave symptom, refusal of food.