The most effective way to reduce a fever is with over-the-counter medications like acetaminophen (Tylenol) or ibuprofen (Advil, Motrin), combined with rest and plenty of fluids. A fever in adults and older children is generally a temperature of 100.4°F (38°C) or higher, measured rectally or at the ear. But before reaching for medication, it helps to understand that fever itself isn’t the enemy. It’s your immune system’s way of fighting infection, and in most cases the goal is comfort, not hitting a specific number on the thermometer.
What Counts as a Fever
The number that qualifies as a fever depends on where you take the temperature. Rectal, ear, and temporal artery readings hit the fever mark at 100.4°F (38°C). Oral readings qualify at 100°F (37.8°C), and armpit readings at 99°F (37.2°C). These differences matter because an armpit reading of 99.5°F might seem mild, but it’s actually equivalent to a higher internal temperature.
Rectal thermometers give the most accurate reading, especially in infants and young children. Oral thermometers are a close second and are more practical for older kids and adults. Ear thermometers are less reliable for babies under 7 months, and forehead thermometers can be thrown off by sweat, direct sunlight, or cold air. If you’re unsure whether someone truly has a fever, oral or rectal is your most trustworthy option.
How Fever-Reducing Medications Work
When your body fights an infection, it produces a chemical messenger called prostaglandin E2 in the brain. This messenger essentially turns up your internal thermostat, telling your body to generate more heat. Both acetaminophen and ibuprofen work by blocking the enzyme that produces this messenger, which brings the thermostat back down toward normal. They take different chemical routes to get there, which is why they can be used together.
Acetaminophen vs. Ibuprofen
Acetaminophen can be given every 4 to 6 hours, with no more than 5 doses in 24 hours. It’s safe for infants 8 weeks and older. Ibuprofen is given every 6 to 8 hours, with no more than 4 doses in 24 hours, but should not be used in babies under 6 months unless directed by a doctor. For adults and children over 12, the daily ceiling is 4,000 milligrams of acetaminophen and 1,200 milligrams of ibuprofen.
Too much acetaminophen can damage the liver, and this risk increases if you drink alcohol while taking it. Too much ibuprofen can harm the kidneys. Stick to the recommended doses, and always dose children by weight rather than age for the most accurate amount.
Alternating the Two
If one medication alone isn’t keeping your fever or discomfort under control, you can alternate between acetaminophen and ibuprofen. The key is not to take both at the same time. Take one first, then switch to the other 4 to 6 hours later, alternating every 3 to 4 hours throughout the day. Research supports that targeting the two different pathways this way provides better relief than either medication alone. If you find yourself alternating for more than three days, that’s a signal to check in with a healthcare provider.
Never Give Aspirin to Children
Aspirin is linked to Reye’s syndrome, a rare but serious condition that causes swelling in the liver and brain. The risk is highest when children or teenagers take aspirin during a viral illness like the flu or chickenpox, but it applies to colds and other viral infections too. This includes any product that contains aspirin as an ingredient, not just plain aspirin tablets. Acetaminophen and ibuprofen are the safe alternatives for kids.
Non-Medication Approaches
Staying hydrated is one of the most important things you can do during a fever. For every degree above 100.4°F, your body loses roughly 10% more fluid than normal through the skin. That adds up quickly, especially in small children. Water, diluted juice, broth, and oral rehydration solutions all work. If you or your child can’t keep fluids down, that becomes an urgent concern on its own.
Lightweight clothing and a comfortable room temperature help your body release excess heat. A lukewarm sponge bath can speed up initial cooling, but the evidence suggests it doesn’t outperform medication over a couple of hours. In one study comparing acetaminophen alone to acetaminophen plus a 15-minute tepid sponge bath, the sponge-bathed children cooled faster in the first hour but showed no meaningful temperature difference by two hours. They did, however, score significantly higher on discomfort. So if a lukewarm cloth on the forehead feels soothing, go for it, but don’t force a full sponge bath on a miserable child expecting dramatic results.
Avoid ice baths or rubbing alcohol on the skin. Ice baths can cause shivering, which actually raises your core temperature. Rubbing alcohol can be absorbed through the skin and is toxic, especially for children.
Fevers in Babies and Young Children
The rules are stricter for infants. Any fever in a baby younger than 3 months requires a call to the doctor, regardless of how the baby seems otherwise. For babies 3 to 6 months old, contact a provider if the temperature reaches 100.4°F or if the baby seems unusually unwell at any temperature. Between 6 and 24 months, a fever over 100.4°F that persists beyond one day warrants a call.
Beyond the thermometer reading, watch for these warning signs at any age: difficulty breathing, skin or lips that look blue, purple, or gray, excessive sleepiness or difficulty waking, a floppy or unresponsive demeanor, inconsolable crying, or a rash that appears suddenly, blisters, or looks infected. These symptoms need prompt medical attention regardless of the temperature.
When a Fever Doesn’t Need Treating
A low-grade fever in an otherwise alert, hydrated adult or older child often doesn’t need medication at all. The fever is doing useful work, making your body a less hospitable environment for viruses and bacteria. The real question isn’t “how high is it?” but “how miserable are you?” If you’re uncomfortable, achy, or unable to sleep, bringing the temperature down makes sense. If you feel okay, it’s fine to let the fever run its course while staying hydrated and resting. For most healthy adults, a fever under 103°F that lasts fewer than three days is typically manageable at home.