A temperature strip, often called a fever strip, is a quick, non-invasive device designed to give a rapid estimate of body surface temperature. This tool is used for initial screening to determine if a fever may be present, rather than providing a precise measurement of the body’s core temperature. Understanding how to use and interpret this device correctly is important for getting the most accurate reading possible from this convenient home screening tool.
The Science Behind Temperature Strips
Temperature strips function based on the principles of thermochromism, utilizing specialized liquid crystals embedded within the plastic film. These liquid crystals change their molecular structure in response to temperature fluctuations. This molecular rearrangement alters the way the material reflects light, which the eye perceives as a color change.
Each temperature reading on the strip corresponds to a specific formulation of liquid crystals that reflects a particular color at that temperature point. This color change is a physical reaction, making the strip a passive, heat-sensitive indicator. The strip converts the skin’s surface temperature into a visual display without requiring batteries or electronic components.
Proper Application for Accurate Results
For a temperature strip to work effectively, it must be placed directly onto a clean, dry surface of the skin to ensure optimal heat transfer. Press the strip flat against the center of the forehead, which is the most common placement area. Ensure the entire heat-sensitive portion of the strip makes firm, uninterrupted contact with the skin.
Hold the strip in this position for the manufacturer’s recommended duration, typically about 15 seconds, allowing time for the liquid crystals to stabilize and react. Holding the strip loosely or moving it around can lead to inaccurate results by preventing sufficient temperature transfer. Environmental factors like a strong draft or sweat can also quickly cool the skin, potentially misleading the reading.
Interpreting the Temperature Display
Reading a temperature strip involves observing which number on the scale is associated with a distinct color change, most often green. The correct temperature is indicated by the colored number that appears brightest or most solid. If two adjacent numbers show color, the actual temperature is estimated to be halfway between those two marked values.
Some strips use a three-color system for finer detail. For example, green indicates the exact temperature, blue indicates the reading is slightly higher than the marked number, and tan or reddish-brown indicates the reading is slightly lower. A fever is indicated when the temperature reads at or above \(100.4^\circ \text{F}\) (\(38^\circ \text{C}\)).
Reliability and When to Use an Alternative
A temperature strip measures skin temperature, which is a peripheral reading and not the body’s core temperature. Because of this, these strips are best utilized as a screening device to give a preliminary indication of a fever. Studies have shown that temperature strips have low sensitivity for detecting fever, meaning they may fail to identify a fever in many cases.
Their precision can be affected by factors like ambient temperature, direct sunlight, or a recent cold compress on the forehead. For situations requiring an accurate measurement, such as for infants or immunocompromised individuals, the reading should be confirmed with a more precise instrument. A digital oral, tympanic (ear), or rectal thermometer provides a measurement closer to the body’s true core temperature and should be used to verify any concerning strip reading.