The axillary method measures temperature under the armpit and is a popular, non-invasive way to check for fever. This technique is common for monitoring temperature in infants and young children because it is safe and straightforward. Although it does not measure the body’s true core temperature, the axillary reading provides a convenient screening tool without causing discomfort.
The Step-by-Step Technique for Axillary Measurement
Before beginning the measurement, ensure the armpit is completely dry. Any moisture can cause a falsely low reading due to evaporative cooling. If the person has recently bathed or exercised, wait 15 to 20 minutes to allow the skin temperature to stabilize. Use a digital thermometer, which is the recommended type, and turn the device on, checking that the display is clear.
Place the tip of the thermometer directly into the center of the armpit, ensuring it contacts bare skin and is not resting on clothing. This location, a small pocket where the skin folds, helps guarantee the most accurate surface reading. Once positioned, the arm must be held down tightly against the body to secure the device and trap heat.
Hold the arm in this snug position until the digital thermometer signals completion, typically with a beep. This signal indicates the device has registered a stable temperature reading. After the signal, remove the thermometer and read the result displayed on the screen.
Interpreting Axillary Temperature Readings
The number displayed after an axillary measurement is a surface skin temperature, which is naturally lower than the core body temperature. A normal axillary temperature falls in the range of 96.6°F to 98.0°F (35.9°C to 36.7°C). This reading requires adjustment to approximate a more accurate internal temperature.
Healthcare providers advise adding between 0.5°F and 1.0°F to the axillary reading to estimate the corresponding oral or rectal temperature. For example, if the thermometer displays 98.0°F, the estimated core temperature would be between 98.5°F and 99.0°F. This adjustment accounts for the measurement being taken on the body’s exterior skin rather than an internal site.
A fever is suspected when an axillary reading reaches 99.0°F (37.2°C) or higher. This temperature threshold is specific to the axillary method and differs from the fever definition for oral or rectal temperature. When recording the temperature, note the time of day and the method used.
Accuracy and Situational Use
The axillary method is considered the least reliable of the common temperature measurement sites because it records peripheral skin temperature rather than core body temperature. Factors like sweating or a cold environment can easily influence the reading, potentially leading to an inaccurate result. The difference between axillary and core temperatures can increase when a fever is present, making the reading less dependable for precise diagnosis.
Despite its lower accuracy, this non-invasive technique is preferred for monitoring temperature trends, especially in newborns, infants, and young children. For these groups, other methods like rectal or oral measurements may be impractical or unsafe. It serves as an initial screening tool for a possible fever in a home setting.
If an axillary temperature indicates a fever, it should be confirmed with a more accurate method, such as a rectal or oral thermometer, if the situation allows. Rectal temperature remains the gold standard for reliably detecting fever in infants and young children. The underarm method is best suited for quick checks and establishing a baseline for routine monitoring.