A fever indicates a temporary rise in body temperature. It is a symptom, not a disease, indicating an active immune response working to fight off perceived threats. Accurate detection helps in managing health and understanding the body’s condition.
Understanding Fever
Normal body temperature is around 98.6°F (37°C), though this can vary slightly among individuals and throughout the day, fluctuating with activity levels or menstrual cycles. Infants and young children naturally exhibit slightly higher body temperatures compared to older children and adults.
The body raises its temperature as a defense mechanism, a process known as pyrexia. This elevation is triggered by substances called pyrogens, such as bacteria, viruses, or those released by immune cells. Raising core body temperature inhibits pathogen growth and activates immune cells, enhancing the body’s ability to fight infection.
A fever often presents with other symptoms. These include chills and shivering, followed by sweating. Other common signs include headache, muscle aches, fatigue, loss of appetite, and general weakness.
Common Detection Tools
Digital thermometers are widely used and employ electronic heat sensors to measure body temperature. They can be used orally, rectally, or in the armpit. The temperature is displayed on a digital screen, providing a quick reading, often in less than a minute.
Temporal artery thermometers scan the forehead to measure temperature. They use infrared sensors to detect heat from the superficial temporal artery. These non-contact thermometers are convenient for quick readings.
Tympanic, or ear, thermometers use infrared technology to measure temperature inside the ear canal. Proper positioning towards the eardrum is necessary for accuracy. They are quick and comfortable for older children and adults.
Axillary thermometers measure temperature by placing the device in the armpit. The thermometer is held under the arm until a stable reading is obtained. While convenient, axillary readings are less accurate than those from other sites.
Rectal thermometers are used for taking temperatures in the rectum. This method is highly accurate because it measures core body temperature directly. The thermometer is gently inserted into the rectum until a reading is displayed.
Selecting the Optimal Detection Method
The choice of thermometer depends on the individual’s age and the desired level of accuracy. For infants younger than three months, a rectal temperature is the most accurate method for assessing core body temperature. While potentially uncomfortable, its precision is recommended for this age group.
For babies and toddlers between three months and three years, rectal temperatures remain a highly accurate option. However, temporal artery thermometers are also recommended for their ease of use and reasonable accuracy, offering a less invasive alternative. Pacifier thermometers can also provide reasonably accurate readings for this age group.
Children aged four years and older, as well as adults, can reliably use oral digital thermometers, provided they can keep their mouth closed and the thermometer properly positioned under the tongue. It is advisable to wait at least 15 minutes after eating or drinking before taking an oral temperature to avoid skewed results.
Temporal artery thermometers are also suitable for children of all ages and adults, offering quick and non-invasive readings. While accurate, factors like direct sunlight, cold temperatures, or a sweaty forehead can influence their readings. Ear thermometers are appropriate for infants older than six months, older children, and adults, but require careful positioning for accuracy.
Armpit temperatures are the least accurate method because they do not measure the internal body temperature directly. If an axillary reading is taken, it often runs about 0.5°F to 1°F (0.3°C to 0.6°C) lower than an oral reading, and a degree or more should be added for a more precise estimation.
Interpreting Readings and Seeking Medical Guidance
A fever is defined as an oral temperature of 100.4°F (38°C) or higher. Rectal and ear temperatures measure about 1.0°F (0.6°C) higher than oral readings, while skin thermometers, such as forehead devices, measure about 1.0°F (0.6°C) lower.
For infants under three months old, any rectal temperature of 100.4°F (38°C) or higher warrants immediate medical attention. For children between three and six months, contact a healthcare provider if their rectal temperature is higher than 102°F (38.9°C), or if they seem unusually irritable or sluggish with a lower temperature.
Children between seven and 24 months old with a rectal temperature above 102°F (38.9°C) that persists for more than a day, without other symptoms, should also prompt a call to their pediatrician. If additional symptoms like a runny nose, cough, or diarrhea are present, seeking guidance sooner may be appropriate.
Adults should contact a healthcare provider if their temperature reaches 103°F (39.4°C) or higher. Immediate medical attention is necessary if a fever is accompanied by severe symptoms such as a severe headache, stiff neck, rash, unusual sensitivity to light, mental confusion, persistent vomiting, difficulty breathing, or seizures.