Perception › Hallucination

Gustatory Hallucination

A gustatory hallucination is tasting something with no food, drink, or substance present to account for it. It commonly presents as a persistent metallic, bitter, or otherwise unpleasant taste, and, because taste and smell are so closely linked, it often occurs together with an olfactory hallucination.

This has traditionally been treated as one of the least common of the hallucination types by sense, and, like olfactory hallucination, its appearance has been considered a prompt to look carefully for a physical or organic contributing cause.

Also known as

Phantageusia

The general medical term for a taste hallucination.

Recognition features

• A taste is experienced with nothing in the mouth that could produce it
• Frequently described as metallic, bitter, or otherwise unpleasant
• Often reported alongside a smell that isn't there, given how closely the two senses interact
• May be linked by the patient, rightly or wrongly, to being poisoned

Eliciting it at interview

• Ask plainly: "Do you ever notice a taste in your mouth that doesn't seem to come from anything you've eaten or drunk?"
• If a poisoning belief accompanies the taste, explore it carefully, since this combination sometimes reflects a persecutory delusion rather than, or in addition to, a straightforward perceptual experience
• Ask about timing in relation to meals to help rule out a simple, ordinary aftertaste

Distinguishing features

• Differs from an ordinary unpleasant aftertaste following food, medication, or illness, which has a real cause
• Often paired with, but conceptually distinct from, olfactory hallucination
• Differs from a delusional belief that food has been poisoned, where the food may taste entirely normal but is believed, on other grounds, to be contaminated

Common misconceptions

• That an unusual taste always signals a physical illness rather than ever being hallucinatory; the two possibilities are not mutually exclusive and both deserve consideration
• That gustatory hallucination is a trivial symptom; when linked to a belief about poisoning it can significantly affect eating and physical health

Related phenomena

Hallucination · Olfactory Hallucination

Practice this

A patient reports a persistent, unpleasant metallic taste in her mouth despite having eaten or drunk nothing, occurring alongside a smell of something burning that nobody else can detect. What is the taste symptom, specifically? · A patient reports smelling burning rubber throughout the day, with no accompanying taste symptom at all, and no external source anyone else can identify. Before revealing the answer: is this a gustatory hallucination? · A patient reports both an unusual taste and an unusual smell with nothing present to account for either. Before revealing the answer, decide what distinguishes a gustatory hallucination from an olfactory hallucination. · You suspect a gustatory hallucination in a patient. Before revealing the answer, decide how you would assess for this. · Explain why a gustatory hallucination is described as often occurring together with an olfactory hallucination, despite being conceptually distinct from it.

Illustration

A 52-year-old man tells his GP that everything has tasted faintly of metal for the past ten days, even water. He has not changed his diet or medication, and initially assumed it was a dental problem before mentioning, almost reluctantly, that he sometimes wonders if someone might be putting something in his food, though he says he isn't sure this makes sense.

References

• Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 3, 'Disorders of Perception'.