Vomiting does not reduce a fever in any meaningful or lasting way. While you might notice a slight temperature dip after vomiting, this is a surface-level change driven by sweating and blood flow shifts, not a reset of the fever itself. In fact, the fluid loss from vomiting can make a fever harder for your body to control, potentially pushing your temperature higher over time.
Why It Feels Like Vomiting Helps
There’s a real physiological reason people associate vomiting with feeling cooler. The nausea response triggers increased blood flow to the skin and sweating, both of which release heat. Research on nausea-related temperature changes shows this is a coordinated response: your body dilates blood vessels near the skin’s surface and reduces internal heat production, temporarily lowering core temperature. That brief cool, clammy feeling after vomiting is real, but it’s a side effect of the nausea process, not a correction of the fever.
The distinction matters. A fever is set by your brain’s thermostat, which raises your target body temperature in response to infection. Vomiting doesn’t change that thermostat setting. Within minutes to an hour, your body works to bring your temperature back up to the new set point, and the brief cooling effect disappears.
The Historical Roots of the Myth
The belief that vomiting can “purge” a fever has deep historical roots. In 19th-century medicine, doctors routinely induced vomiting, sweating, and other forms of purging to treat fevers and infections. The theory was that illness came from harmful poisons or overstimulation of the nervous system, and forcing the body to expel fluids would relieve the cause. Doctors prescribed medicines specifically designed to trigger vomiting as a fever treatment. This approach was abandoned as modern medicine developed a clearer understanding of infection and immune response, but the intuition that expelling something from the body should help with fever has lingered in popular thinking.
Vomiting Can Actually Make Fever Worse
The bigger concern is what vomiting takes away: fluid. Your body needs adequate hydration to regulate temperature effectively, and vomiting strips fluid rapidly. Animal research has demonstrated this clearly. Dehydrated subjects run higher fevers that last longer and follow a more erratic pattern, with increased blood vessel constriction that traps heat inside the body. The natural cooling mechanisms your body uses to cap a fever simply don’t work as well when you’re low on fluids.
The reverse is also true. In the same research, rehydrating the subjects significantly lowered both temperature and heart rate during fever. Fluid supplementation plays a direct, measurable role in keeping body temperature lower. This means that repeated vomiting without adequate fluid replacement creates a cycle where fever becomes harder to break.
Why Fever and Vomiting Often Appear Together
If you’re searching this question, you’re likely dealing with both symptoms at once. That’s common. Viral gastroenteritis, often called “stomach flu,” typically causes watery diarrhea, abdominal cramping, nausea or vomiting, and sometimes fever. Influenza and other viral infections can also produce both symptoms simultaneously. The vomiting isn’t your body’s attempt to fight the fever. They’re parallel symptoms of the same underlying infection, driven by different mechanisms.
In gastroenteritis, vomiting usually peaks in the first 24 to 48 hours and tapers off, while fever may persist a bit longer. One symptom doesn’t resolve the other. They follow their own timelines as your immune system clears the infection.
Managing Fever When You Can’t Keep Medicine Down
The practical challenge of having both fever and vomiting is that you may not be able to swallow or hold down fever-reducing medicine. If oral medication comes back up within minutes, it likely hasn’t been absorbed. For children over 6 months, fever-reducing suppositories offer an alternative. These are inserted rectally and bypass the stomach entirely, delivering the same active ingredient without relying on your ability to keep anything down. They’re given every 4 to 6 hours, with a maximum of 4 to 5 doses in 24 hours depending on the child’s age. Adults can also use suppository forms of common fever reducers, available at most pharmacies.
Timing matters too. If you can identify a window between vomiting episodes, taking oral medicine during that gap gives it time to absorb. Even 20 to 30 minutes of keeping a dose down is usually enough for partial absorption.
Staying Hydrated Is the Real Priority
Since dehydration directly worsens fever, replacing lost fluids is more important than chasing the number on the thermometer. When vomiting is active, the key is small amounts frequently rather than large gulps. Oral rehydration solutions, which contain a precise balance of salt and sugar to maximize absorption, are recommended at 50 to 100 milliliters per kilogram of body weight over four hours during moderate dehydration, with extra given to replace each episode of vomiting or diarrhea.
In practice, this means sipping a tablespoon or two every few minutes rather than drinking a full glass. Your stomach tolerates small, steady volumes far better than large ones when it’s irritated. If vomiting is so severe that no fluid stays down at all, or if there are signs of significant dehydration, intravenous fluids may be necessary.
Signs of dehydration to watch for include no urination for 8 hours, crying without tears, a dry mouth and tongue, and unusual fatigue or weakness. In infants, a sunken soft spot on the head is a notable warning sign. These indicate fluid loss has outpaced what the body can compensate for.
What Actually Brings a Fever Down
Fever resolves through two paths. The first is your immune system successfully fighting the infection, which lowers the brain’s temperature set point back to normal. This happens on its own timeline and can’t be rushed by vomiting or any other purging method. The second is fever-reducing medication, which chemically lowers the set point temporarily, providing comfort while your body continues its work.
For context, a low-grade fever sits between 99.1 and 100.4°F (37.3 to 38.0°C), moderate fever ranges from 100.6 to 102.2°F (38.1 to 39.0°C), and high-grade fever runs from 102.4 to 105.8°F (39.1 to 41.0°C). Low and moderate fevers in otherwise healthy people often don’t need aggressive treatment at all. The fever itself is part of the immune response, creating an environment that’s less hospitable to viruses and bacteria. The goal of management is comfort and hydration, not eliminating the fever entirely.