The axillary method remains one of the most common approaches for monitoring body temperature, particularly in home settings and pediatrics. This non-invasive technique involves taking a reading from the armpit, offering a simple way to screen for temperature changes. Understanding the proper technique and the limitations of this method is important for accurate interpretation, especially since other methods like oral or rectal readings may be challenging in young children.
Where and What Axillary Temperature Measures
Axillary temperature is the reading taken from the area beneath the arm, known as the axilla or armpit. This method involves placing a thermometer directly against the skin to capture a localized surface temperature reading. This reading is an approximation of the body’s internal, or core, temperature.
The armpit is chosen due to its easy accessibility and relative safety compared to internal methods like rectal readings. When the arm is held close to the body, the enclosed space traps heat. This stabilization allows the thermometer to measure a temperature that correlates with the core body temperature.
Step-by-Step Measurement Technique
Achieving an accurate axillary reading requires careful preparation and proper placement of the thermometer. Before starting, ensure the armpit is dry, as moisture from sweat or a recent bath can cause an artificially low reading. If the person has recently bathed or exercised, waiting at least 15 to 20 minutes allows the surface temperature to normalize.
The digital thermometer should be placed with its tip centered in the armpit, ensuring the metal sensor is in direct contact with the skin and not against clothing. Once positioned, the arm must be held firmly down against the side of the body to create a tight seal over the thermometer. This contact traps the heat and stabilizes the reading.
The thermometer must remain in place until the device signals that the reading is complete, usually indicated by a beep on a digital model. Axillary measurements typically require a longer duration than oral or rectal readings to fully register the temperature. After the beep, the thermometer is removed, and the number is recorded as an axillary reading.
Reliability Compared to Other Methods
Rectal temperature is often regarded as the gold standard for accuracy because it most closely reflects the internal body temperature. In contrast, axillary readings measure a surface temperature and are more susceptible to external factors like ambient room temperature or recent physical activity.
Research indicates that an axillary temperature is typically lower than an oral temperature by about 0.5 to 1.0 degree Fahrenheit, and lower than a rectal temperature by a slightly greater margin. For this reason, some healthcare providers suggest adding a degree to the axillary reading to estimate the core temperature.
The axillary method is often favored for screening or monitoring, especially in infants and toddlers, because it is non-invasive and easy to perform. If a fever is suspected based on an armpit reading, a more accurate method like a rectal or oral measurement may be recommended for confirmation, depending on the person’s age.
Interpreting Normal and Fever Readings
The interpretation of an axillary temperature must account for the fact that it is a surface reading, resulting in a lower normal range than other sites. A normal axillary temperature typically ranges between 96.6°F and 98.0°F (35.9°C and 36.7°C). Readings can naturally fluctuate throughout the day based on activity and time.
An axillary reading is generally considered to indicate a fever when it reaches 99.0°F (37.2°C) or higher. This lower fever threshold reflects the typical difference between the armpit and core body temperature. In infants and young children, an axillary temperature of 99.0°F or above should prompt further observation.
It is advisable to contact a healthcare provider if an infant under three months of age has any temperature reading that suggests a fever, regardless of the measurement site. For all ages, a persistent or significantly high fever warrants medical attention.