Fevers can be scary, and as a mom, I’ve certainly lost sleep worrying about my daughter’s temperature. But as miserable as a fever may feel, it’s comforting to know that it’s a sign the body is working properly by raising its own temperature to fight something off, typically a virus or bacterial infection. Some doctors and medical guides even recommend letting a fever run its course.

In certain populations, fever can be a sign of a more serious infection. It’s important to contact a doctor when fever develops in an infant under 3 months old, or in a person who is immunocompromised, undergoing chemotherapy, recovering from surgery, or who has had a splenectomy. Additionally, a fever that persists longer than three days could be a sign of something more serious.

To learn more about fevers and how to effectively reduce them, we spoke to Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine. We also consulted current research and recommendations from the Mayo Clinic, Harvard Health, and the Centers for Disease Control (CDC).

When to use a fever reducer

The average body temperature is 98.6 degrees, and in both adults and children, a fever is considered to be 100.4 degrees and higher. You may be familiar with the term “low-grade fever,” but this is a misconception. A temperature of 99 degrees is, in fact, a normal temperature variation.

When to start using a fever reducer depends on someone’s comfort level as well as the presence of any underlying conditions, but these are the general guidelines set forth by the Mayo Clinic:

  • Infants, 0 to 3 months: Call a pediatrician for any fever 100.4 degrees and higher.
  • Infants, 3 to 6 months: Call a pediatrician for any fever 102 degrees and higher, and consider using a fever reducer.
  • Infants and toddlers, 6 to 24 months: Consider using a fever reducer at 102 degrees and higher. Call a pediatrician if fever doesn't respond to medication or persists longer than one day.
  • Kids, 2 to 17 years: Consider using a fever reducer above 102 degrees. Call a pediatrician if fever doesn't respond to medication or persists longer than three days.
  • Adults, 17 years and older: Consider using a fever reducer above 102 degrees. Call a doctor if fever doesn't respond to medication or persists longer than three days.
  • Anyone who is immunocompromised or has an underlying medical condition: Call a doctor for any fever.

Generic medications are generally as safe and effective as brand-name drugs. Occasionally, generic drugs made in other countries are found to have contaminants. In these cases, the FDA responds swiftly to remove them from the market.

In addition to treating a fever with medication, it's important to drink plenty of fluids to prevent dehydration. "Fluid intake is always an important part of the treatment of fevers," said McKnight.

How to accurately detect a fever

Try to take readings at the same time each day, as body temperature naturally fluctuates throughout the day. Different techniques can also yield different results, so use the same method each time you record temperature. To get a correct reading, use a trusted thermometer and take three readings to ensure accuracy.

  • Rectal (bottom) temperatures are most accurate for babies and toddlers up to age 3.
  • Temporal artery (forehead) temperatures are accurate for those ages 3 months and older.
  • Oral (mouth) temperatures are accurate for older children and adults.
  • Tympanic (ear) temperatures are usually accurate for older children and adults.
  • Axillary (armpit) temperatures are typically least accurate. Never add or subtract degrees from an axillary reading based on any guidance you may have received.

When to see the doctor

Body temperature is only one piece of information. If you or your child feels particularly ill, that should prompt a call for medical advice. In addition to the recommendations above, contact your doctor under any of the following circumstances:

  • Medication is not bringing the fever down.
  • Fever rises above 104 degrees.
  • Severe headache, stiff neck, or trouble breathing occurs.
  • Seizure occurs. (Note: febrile seizures are relatively common in young children and are usually harmless.)
  • Person with fever is part of an at-risk population or is an infant is under 3 months old, in which case fever is a medical emergency.

The bottom line is if you are experiencing distressing or unusual symptoms or if you are concerned about a fever, don't hesitate to contact your doctor.

Here are our top picks for the best fever reducers:

The best fever reducer for adults

Acetaminophen effectively reduces fever and is less likely than NSAIDs to cause stomach irritation.

Acetaminophen is an antipyretic (fever-reducing) medication that is well tolerated by many people and can be taken every four to six hours. It is not considered a nonsteroidal anti-inflammatory drug (NSAID), so it's an excellent option for people who are unable to take NSAIDs.

Acetaminophen comes in a variety of forms, including tablets, rapid release gels, dissolvable powder, liquid, chewable tablets, and suppositories. It can also be administered intravenously in a hospital setting.

While it is generally well-tolerated, rare but potentially serious side effects include allergic reaction and liver damage. It does not typically irritate the stomach lining or cause stomach problems, which can happen with NSAIDs.

Be sure to talk to your doctor before taking any medication and always adhere to the dosing recommendations on the package.

Pros: Available in a wide variety of forms, stomach irritation is uncommon

Cons: Can cause an allergic reaction or liver damage

The best fever reducer for infants

Foto: Source: Amazon

Acetaminophen is considered safe for infants, and it's easy to administer.

Fevers in infants can be scary, and they should be taken seriously. "In any infant under 2 months of age, a fever could be a medical emergency," said McKnight.

Acetaminophen is our top pick because it is safe and effective as a fever reducer for infants under 6 months old and is easy to administer in its liquid form. Another popular fever reducer, ibuprofen, is not considered safe for infants under 6 months.

Before administering liquid acetaminophen to an infant under 2 months old, consult a pediatrician to ensure there isn't a more serious issue. In older infants, caregivers can administer liquid acetaminophen using the manufacturer's recommended dosage but should still consult a pediatrician.

No fever reducer is going to be effective if you can't get a baby to take it. My 20-month-old daughter actually gets excited when I give her liquid acetaminophen because she likes how it tastes. It comes in a variety of flavors, including grape, cherry, and berry. Tylenol, Little Remedies, and other brands also offer a dye-free option.

Depending on dosing, acetaminophen can be given every four hours. Although it is less likely than ibuprofen to cause stomach irritation, some children may experience nausea or vomiting from any medication.

Potential serious side effects for infants include allergic reaction and liver damage.

Be sure to talk to a child's pediatrician before administering any medications.

Pros: Safe for infants of all ages, comes in a variety of appealing flavors

Cons: Can cause allergic reaction or liver damage

The best fever reducer for children

Foto: Source: Rite Aid

Ibuprofen has been shown to be marginally more effective than other options for reducing fever in kids, and it lasts two hours longer than acetaminophen.

While acetaminophen is effective in children, a few studies (here and here) have shown evidence that ibuprofen might be slightly more effective at reducing fever in kids. However, some illnesses present with fevers that respond to ibuprofen or acetaminophen slightly better, and some children seem to do better with one or the other consistently.

We ultimately chose ibuprofen as the best fever reducer for children because its fever-reducing qualities are effective two hours longer than acetaminophen. Depending on the dose, ibuprofen can be taken every six hours. This extra time can provide caregivers and children with more uninterrupted sleep.

Ibuprofen for children is available as a liquid or a chewable tablet, and brands such as Advil and Motrin offer dye-free options. Common flavors include grape, berry, bubblegum, blue raspberry, fruit, and white grape.

Potential serious side effects include allergic reaction and, although rare in children, stomach bleeding. NSAIDs tend to be harder on the stomach than acetaminophen, so monitor a child for any stomach discomfort.

Be sure to talk to a child's pediatrician before administering any medications.

Pros: May be slightly more effective than acetaminophen for kids, available as liquid and chewable, many flavor options

Cons: May cause stomach upset or allergic reaction

How to accurately take a temperate

Foto: Source: Mandy Major

How to take an accurate rectal temperature

  1. Clean the thermometer with soap and water.
  2. Place a small amount of petroleum jelly on the end.
  3. Place your baby across your lap face down or on their back on a firm surface.
  4. Gently place the thermometer about a half-inch into the anus.
  5. Place your entire hand around the child's bottom, holding the thermometer in place between your fingers.
  6. Hold in place for about one minute or until you hear the beep.

Tip: If you're still wondering how to master this technique, the American Academy of Pediatrics has a useful illustrated guide.

How to take an accurate ear temperature

  1. Clean the probe before/after each use.
  2. Gently pull on the top outermost part of the ear (this is key).
  3. Slowly insert the probe into the ear canal. Do not push.
  4. Press the button to take the temperature.
  5. Remove the thermometer after it beeps.

Tip: Check for earwax buildup before use, and do not use immediately after bathing.

How to take an accurate forehead temperature

  1. Place the probe in the middle of the forehead.
  2. Press the scan button and begin to move slowly to one side.
  3. Move from one ear, over the forehead, and toward the opposite ear.
  4. Release the scan button and remove the thermometer as it beeps.

Tip: It is important to maintain contact with the forehead at all times. The side-to-side motion should take between three and five seconds.

How to take an accurate temperature under the arm

  1. Turn on the thermometer and place the probe in the center of your baby's armpit.
  2. Hold it in place until you hear a beep.

Tip: Ensure the thermometer is touching skin only, not clothing.