Vomiting

body effect

valenceadversefrequencyuncommontemporalacute

AI-inferred — this entry was drafted by AI and has not yet been verified against primary sources. A sourced revision is planned.

Vomiting is the forcible expulsion of stomach contents through the mouth, produced by coordinated contraction of the diaphragm and abdominal musculature.

As a drug effect it is acute and dose-proportional, resolving as the substance wears off; it is distinct from vomiting with an underlying gastrointestinal or systemic cause. It ranges from a single brief episode to repeated purging that leaves the person temporarily depleted.

Vomiting is an uncommon though recognized adverse effect. It is most commonly induced at moderate to high doses under psychedelics such as psilocybin mushrooms, where nausea typically precedes and accompanies it; irritants present in the fungal material contribute additional gastric stimulation alongside the pharmacological trigger, raising the likelihood.

phenomenology

Vomiting is felt as an escalating loss of bodily control: nausea crests into retching, and the diaphragm contracts in one or more forcible heaves. It commonly comes with profuse sweating, pallor, a rapid heartbeat, and a brief sensation of faintness or muscular weakness in its aftermath.

Awareness of the cycle — knowing a further wave may follow — can itself sustain nausea and make the next episode more likely. At higher doses under psychedelics, where the experience is already disorienting, repeated purging can compound the sense that the body is no longer operating normally.

mechanism

Vomiting arises through different pathways depending on the drug class:

Psychedelics — stimulate 5-HT3 receptors in the gastrointestinal tract and the chemoreceptor trigger zone, activating the brainstem's vomiting center; with psilocybin mushrooms, irritants in the fungal material add a direct gastric stimulus on top of this receptor-mediated pathway.

How much each pathway contributes in a given case is not fully understood.

safety

Vomiting is unpleasant and briefly depleting but not dangerous on its own for most people; risk rises when episodes are prolonged or paired with other signs.

If it happens — sit upright or lie on your side to reduce aspiration risk, sip small amounts of water between episodes, and stay still rather than trying to push through the experience.
Seek help if — vomiting continues beyond several hours, blood appears in what is expelled, or it accompanies an inability to keep any fluid down, severe confusion, or rapidly worsening distress.
Higher risk — people with esophageal conditions should be especially cautious; at high doses under psychedelics, persistent vomiting combined with mounting psychological distress is a signal to reduce stimulation and, if symptoms deteriorate, to seek medical support.

variability

Who experiences it, and how strongly, varies widely. Higher doses raise both likelihood and intensity. Consuming psychedelics on an empty or lightly filled stomach reduces gastric irritation; eating heavily beforehand raises it.

Anxiety going in tends to amplify nausea — especially under psychedelics — and a sensitive gag reflex or prior history of motion sickness increases susceptibility. Expectation matters: anticipating nausea strongly can prime it. Going in settled, with a light stomach, is among the most reliable ways to reduce the risk.