When your child feels warm, fussy, or unusually tired, one of the first questions you’ll ask yourself is: “Do they have a fever?” Checking temperature at home is one of the most common ways parents and caregivers monitor health, yet it’s also one of the most confusing. With so many thermometers on the market—rectal, oral, underarm, forehead, ear—it’s hard to know which method gives the most accurate result.
As both a nurse and a mom, I can tell you that not all temperature sites are created equal. Some give you a clear picture of what’s happening in the body, while others are more convenient but less precise. In this guide, we’ll walk through the best way to take a child’s temperature at different ages, the pros and cons of each method, and how to make sure you’re checking fever safely and accurately at home.
Understanding Core vs. Surface Temperatures
Before we compare the different thermometer types, it’s important to understand the difference between core temperature and surface temperature.
- Core temperature refers to the body’s internal temperature, which is the most reliable indicator of fever. The pulmonary artery is a true reflection of core temperature but isn’t a practical site for a temperature since it requires an invasive procedure with specialized equipment. Sites like the rectum and mouth come closest to reflecting true core temperature.
- Surface temperature is measured at the skin level—like the forehead, ear, or underarm. These sites are easier to access but can be influenced by outside factors like room temperature, sweating, or improper placement.
Surface sites can be useful for quick checks, but for medical decisions (like whether to call your doctor or go to the ER), a more reliable method should guide your next step.
Rectal Temperature: The Gold Standard for Infants
For babies under 3 months old, rectal thermometers remain the gold standard for accuracy. Research shows rectal readings most closely reflect a child’s true core temperature, which is why pediatricians and the American Academy of Pediatrics (AAP) recommend this method in infants.
Why rectal is recommended for infants:
- Accuracy matters most in early life. A fever in a newborn can signal a serious infection that requires immediate medical evaluation.
- Other sites can mislead. Axillary (underarm) and forehead readings often underestimate fevers in young babies, which could delay care.
The challenges:
- Rectal temperature checks can feel invasive and uncomfortable, which makes many parents hesitant to use them.
- They require careful technique—using a digital or single-use thermometer designed for rectal use, with gentle insertion and supervision at all times.
Because of these concerns, parents sometimes avoid rectal checks altogether. But for infants under 3 months, it’s the most reliable way to know if your child needs urgent medical attention. If you’re unsure about technique, ask your pediatrician to demonstrate safe use during a well-baby visit.
Oral Temperature: Reliable for Older Kids and Adults
Once children are around 4–5 years old and able to hold a thermometer under their tongue without fidgeting, oral temperature checks become a reliable option.
Why oral works well:
- Oral readings closely approximate core temperature when used correctly.
- They’re comfortable for most kids and adults.
- They’re fast and convenient in daily use.
What to watch out for:
- Food or drink can affect the reading. Wait at least 15 minutes after eating or drinking before checking.
- Younger kids may not keep the thermometer in place long enough for an accurate result.
- Mouth breathing, coughing, or crying can also interfere.
For older children, teens, and adults, oral readings are usually the preferred method—offering a balance of accuracy, comfort, and ease.
Axillary (Underarm) Temperature: Comfortable and Practical
Axillary temperature checks are one of the easiest and most comfortable ways to monitor a child’s temperature—especially for toddlers or children who resist other methods. The underarm site is non-invasive, quick, and often used for screening at home, in schools, or in daycare settings.
Why axillary readings differ
Underarm temperatures tend to register slightly lower than oral or rectal readings because the thermometer measures heat from the skin’s surface rather than inside the body. To better approximate internal temperature, many clinicians recommend adding about ½ to 1 °F (0.3 to 0.6 °C) to the result.
For example, if your child’s axillary thermometer shows 99 °F (37.2 °C), adding a degree brings the adjusted temperature closer to 100 °F, which approaches the threshold for a true fever (100.4 °F / 38 °C). This makes axillary checks a practical baseline for tracking trends over time, even if they run a little lower than other methods.
If your child feels unwell or their underarm temperature seems borderline, you can confirm it with an oral or rectal check for greater precision. And for families focused on hygiene, single-use thermometers like NexTemp® make underarm checks simple, accurate, and germ-free—no cleaning or shared devices required.
Tympanic (Ear) and Temporal (Forehead) Thermometers: Convenience vs. Accuracy
Ear and forehead thermometers are popular with families because they’re fast, non-invasive, and easy to use—even while a child is sleeping. But while they win points for convenience, their accuracy can vary.
Tympanic (ear) thermometers:
- Pros: Provide results in seconds, tolerated well by older babies and children.
- Cons: Accuracy depends heavily on correct placement. Earwax, small ear canals, or improper positioning can all lead to incorrect readings.
Temporal (forehead) thermometers:
- Pros: Easy to swipe across the forehead or aim at the temporal artery for a fast reading.
- Cons: Accuracy may be influenced by sweat, air flow (like fans or open windows), or distance of the device from the skin.
Both tympanic and temporal methods can be helpful for quick checks, especially at night. However, if you need a precise reading to decide whether to call your pediatrician, rectal (for infants) or oral (for older kids and adults) are more reliable.
Safe and Accurate Fever Checks at Home
Checking temperature regularly during illness gives parents and caregivers valuable information. A consistent fever log helps you track whether symptoms are improving or worsening—and makes it easier to decide when to call a healthcare provider.
The challenge is doing this safely and accurately. Reusable thermometers need careful cleaning after every use, and studies have shown that improperly disinfected devices can transmit harmful germs. That’s not a risk most families want to take.
This is where single-use thermometers like NexTemp® stand out.
- Clinical accuracy: NexTemp® thermometers use the same liquid crystal technology trusted by hospitals worldwide. Clinical studies show they provide precise, reliable readings that meet or exceed clinical standards—equivalent in performance to traditional mercury thermometers, without the risks.
- Infection control: Because they are single-use and individually wrapped, there is no need for reprocessing or disinfecting. This design eliminates the risk of cross-contamination between family members.
- Convenience at home: No batteries, no probe covers, no harsh cleaning supplies required. They’re compact, disposable, and easy to keep on hand for kids or older adults.
- Trusted worldwide: Medical Indicators’ thermometers have been used for decades in hospitals and healthcare facilities, with more than a billion sold globally. That same professional-grade performance is now available for families at home.
For parents, this means you can monitor fever confidently without the stress of cleaning or the worry of spreading germs. For caregivers, it means keeping infection control at the forefront while still getting clinically accurate readings to guide care decisions.
Key Takeaways for Parents and Caregivers
- Rectal readings are the most accurate for infants under 3 months, while oral thermometers are the best option for older children and adults.
- Axillary thermometers are comfortable and convenient but tend to read slightly lower than rectal or oral methods—making them a good choice for children under 5 when those options aren’t practical.
- Ear and forehead thermometers are quick and non-invasive but can give less consistent results, so they’re best used for screening rather than clinical decision-making.
- Accurate fever checks are critical for knowing when to seek medical care and how to manage illness at home.
- Single-use thermometers like NexTemp® combine professional-grade accuracy with infection control, eliminating cross-contamination risks and simplifying fever checks for families and caregivers.
| Accurate Temperature Measurement (Clinically Accurate)Ranked in order, 1 is best | ||||
| Site | Under 3 months | Under 5 years | 5 years + | Adult |
| 1. Rectal | ✔️ | ✔️ | ✔️ | ✔️ |
| 2. Oral | X | X | ✔️ | ✔️ |
| 3. Axillary | X | ✔️ | ✔️ | ✔️ |
| 4. Ear | X | X | X | X |
| 5. Forehead | X | X | X | X |
| Temperature Screening (Quick Check) | ||||
| Site | Under 3 months | Under 5 years | 5 years + | Adult |
| Oral | X | X | ✔️ | ✔️ |
| Forehead | X | ✔️ | ✔️ | ✔️ |
| Ear | X | X | ✔️ | ✔️ |
At the end of the day, the best way to take a child’s temperature is the method that balances accuracy, safety, and practicality for their age. With the right tools, you can check fevers confidently, protect against germs, and focus on what matters most—helping your child or loved one feel better.
FAQs
What is the most accurate way to check a baby’s temperature?
For infants under 3 months, rectal thermometers are considered the gold standard. Pediatricians rely on rectal readings because they best reflect a baby’s core temperature.
At what age can I switch from rectal to oral thermometers?
Most children can reliably use an oral thermometer around 4–5 years old, when they’re able to hold it under the tongue without moving or talking.
Are forehead or ear thermometers accurate for kids?
They’re quick and non-invasive, but research shows they can be affected by sweat, room temperature, placement, or earwax. They’re useful for screening but less reliable for medical decisions.
How often should I check my child’s temperature when they’re sick?
There’s no set rule—check when symptoms change, before giving fever-reducing medicine, and if you’re concerned. Consistent, hygienic checks help you track progress and know when to call your doctor.
What’s the safest thermometer for families?
Single-use thermometers like NexTemp® reduce the risk of cross-contamination while providing clinically accurate readings, making them a safe option for households with children or older adults.
609-737-1600