Vomiting is one of the most common side effects of alcohol poisoning and of a drug overdose. It happens because the body tries to remove toxic substances.
But not everyone throws up when they experience one or both of these episodes. The reason is because people have different stomach irritation thresholds, meaning they may not produce acid that triggers vomiting. Likewise, they may have different tolerance levels and a suppressed gag reflex. The type of alcohol and the drug also play a role in whether a person vomits or not.
Let’s take a look at why alcohol poisoning or drug overdose causes vomiting, and why not everyone is affected.
Why Do We Vomit?
Emesis is the medical term for vomiting. When you vomit, muscles in your stomach, chest, neck, and head contract to force the content of your stomach up and out through your mouth. Vomiting takes place in four steps:
- Decisions in the brain. A specialized area in your brain detects distress signals and toxins in the body. It makes a decision whether to vomit or not.
- You feel nauseous. You may be dizzy, your vision may feel like it’s spinning, and you may sweat.
- Retching. Your muscles contract and you dry heave, acting out vomiting without any stomach content coming up.
- Vomiting. Your stomach contents are forced up into your esophagus and out of your mouth.
Vomiting is a protective system. We do it when we have something in our internal system that is considered dangerous or that the body doesn’t know how to process [1]. Vomiting happens mostly when we eat food that has harmful bacteria or when we’re sick. Pregnancy, motion sickness, anxiety, and migraines can also cause vomiting.
Why Do Some People Vomit and Others Don’t?
Vomiting is common in alcohol poisoning and drug overdoses, but it doesn’t happen for everyone. This may be because of:
- Suppressed reflexes. Alcohol and depressants such as opioids and sedatives can affect or switch off the brain’s ability to signal that vomiting needs to happen.
- Substance type. Pure opioids and other substances don’t sufficiently irritate the stomach lining to provoke the vomit response.
- Genetics. Differences in liver enzymes, stomach tolerance, and baseline nervous system sensitivity contribute to vomiting thresholds and processes in different ways.
- Method of consumption. If a drug is injected, smoked, or snorted, it can bypass the digestive tract and not trigger a vomiting reaction.
How Does Vomiting Help With Alcohol Poisoning or Drug Overdose?
To understand how vomiting helps with alcohol poisoning and drug overdose, we need to separate the events and understand each of them individually.
Alcohol poisoning is when someone consumes large amounts of alcohol in a short space of time. High volumes of alcohol in the bloodstream mean areas of the brain that control breathing, heart rate, and other basic life-support functions slowly stop working. Alcohol poisoning can cause permanent brain damage or death: in the US, 2,200 people die from it every year [2].
Vomiting is a symptom of alcohol poisoning. The brain detects high levels of alcohol and sends chemical signals to the stomach to empty. If you drink alcohol too fast for the body to process it, there is a buildup of toxins that vomiting attempts to eliminate. Alcohol also irritates your stomach lining and increases acid production, leading to inflammation and nausea that trigger vomiting.
A drug overdose is when a person uses more of a substance than their body can handle. It can also happen if a person mixes drugs that overwhelm the body. Currently, fentanyl is the drug with the highest rates of overdose in the US [3].
Vomiting is a sign of a drug overdose. Similar to alcohol poisoning, the brain identifies that a dangerous volume of a substance is present, and takes action to rapidly expel it in order to survive. Many substances slow how the gastrointestinal tract functions, which causes delayed gastric emptying and a backup of fluids that force the body to vomit. And, drug overdose can change the body’s balance and spatial orientation, producing motion sickness or vertigo that adds to the need to vomit.
Can Vomiting Be Dangerous?
Yes. Although vomiting is a natural reflex to protect the body when it is under internal threat, vomiting while experiencing alcohol poisoning or a drug overdose comes with risks.
Choking is the biggest threat. If the person is unconscious or so impaired they can’t hold their head up, they are at risk of choking on their vomit. An overdose or alcohol poisoning can depress the central nervous system, which suppresses the body’s gag reflex, meaning a person cannot swallow or clear their airways and can suffocate while vomiting.
A person may also inhale vomit into their lungs during alcohol poisoning or a drug overdose. This can introduce stomach acid and bacteria into the lungs and lead to chemical pneumonitis or severe lung infections.
If you see someone vomiting due to alcohol poisoning or a drug overdose:
- Immediately lay them on their side in the recovery position.
- Keep their mouth and nostrils uncovered, and ensure vomit does not build up around their mouth, blocking their airway.
- Do not give them anything to drink or eat.
- Stay with them and call emergency services straight away.
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Sources
[1] Horn, C. 2009. Why is the neurobiology of nausea and vomiting so important?. Appetite.
[2] National Center for Drug Abuse Statistics. 2025. Alcohol Related Deaths. drugabusestatistics.com.
[3] Garnett, MF, et al. 2026. Drugs Most Frequently Involved in Drug Overdose Deaths: United States, 2017–2023. National Vital Statistics Reports.