Forehead thermometers, also known as temporal artery or non-contact infrared thermometers, offer a quick and non-invasive way to screen body temperature. Their popularity stems from the ability to take a measurement rapidly without touching the skin, which helps minimize the risk of spreading illness. Proper technique is necessary to ensure the device provides the most accurate reading possible. Understanding the factors that influence their measurement is key to correct usage.
How Forehead Thermometers Measure Heat
These specialized devices utilize infrared technology to measure the thermal energy naturally emitted from the skin surface. The thermometer targets the area over the temporal artery, a blood vessel running just beneath the skin across the forehead to the temple. This artery provides a consistent blood supply that closely reflects the core body temperature. The infrared sensor captures this heat signature and uses an internal algorithm to convert the surface temperature reading into an estimate of core body temperature.
Step-by-Step Guide to Taking a Temperature
Before beginning, ensure the thermometer is ready by checking that the batteries are charged or fresh and that the sensor lens is clean. If the device was stored in a much colder or warmer location, allow it to acclimate to room temperature for 10 to 30 minutes. Confirm the device is set to the correct body temperature mode, as many have a separate mode for measuring surface temperatures of objects.
Preparation
Prepare the person being measured by ensuring the forehead area is unobstructed; this means removing hats, scarves, or hair that covers the temple. The skin should be clean and dry, as sweat or heavy makeup can interfere with the infrared reading. The person should ideally be still for a few minutes before the measurement is taken.
Non-Contact Models
For non-contact models, hold the thermometer perpendicular to the center of the forehead, aiming at a distance specified by the manufacturer, typically between one to two inches (3 to 5 cm). Maintain a steady hand and a direct angle, avoiding sideways or slanted positioning. Press and hold the scan button, waiting for the device to beep or display the final temperature reading.
Contact Models
If using a contact temporal artery model, place the probe gently on the center of the forehead and lightly slide it straight across the forehead toward the hairline near the ear. Keep the scan button depressed throughout the entire slow movement until the device indicates the measurement is complete. Taking multiple readings and noting the highest temperature is a common practice to confirm the result.
Avoiding Inaccurate Readings
External and physical factors can compromise the accuracy of a forehead thermometer reading. Environmental conditions like drafts, direct sunlight, or proximity to a radiant heat source can skew the measurement. The device should be used in a draft-free space and within a typical room temperature range, often between 60.8°F and 104°F (16°C and 40°C).
Physical interference on the skin is a major source of error. Sweat, moisture, or certain facial cleansers can cause the skin surface to cool or reflect heat differently. If the person is visibly sweating, the reading may be artificially lowered; wait until the forehead is dry or measure behind the earlobe if permitted by the manufacturer. Moving the device too quickly during a scan or not waiting a few seconds between successive measurements can also result in unreliable data.
Interpreting the Temperature Reading
The temperature displayed by a forehead thermometer is generally an estimate of the body’s core temperature, but its normal range is slightly different from an oral or rectal reading. Forehead readings are often about 0.5°F to 1.0°F (0.3°C to 0.6°C) lower than a standard oral temperature. A typical body temperature for a healthy person ranges from approximately 97.0°F (36.1°C) to 99.0°F (37.2°C), but this fluctuates throughout the day.
For most adults and children, a temperature reading of 100.4°F (38°C) or higher, as measured by a temporal artery thermometer, is generally considered a fever. The definition of a fever can vary based on the measurement method. Always consider the age of the person, as a fever in an infant under three months of age is a greater concern than in an older child or adult. The presence of other symptoms, such as chills or fatigue, should also be considered alongside the numerical reading.