A fever is a temporary increase in your body’s temperature, typically above 98.6°F (37°C). It signals that your body is actively combating an infection. This elevated temperature is a regulated physiological response orchestrated by the brain’s hypothalamus, which acts as the body’s thermostat.
How Fever Supports Your Immune System
When pathogens like bacteria or viruses enter the body, the immune system releases chemical messengers called pyrogens. These pyrogens travel to the hypothalamus, prompting it to raise the body’s temperature set point. This adjustment creates an environment less favorable for the growth and replication of many microorganisms, as human pathogens typically thrive at normal body temperatures around 98.6°F (37°C). An increase of just 1-4°C can help fight many infections by directly reducing pathogen proliferation.
The elevated temperature also significantly boosts the activity and production of various immune cells. Fever stimulates the bone marrow to produce more white blood cells, the primary defenders against invaders. It also enhances the proliferation, maturation, and activity of these cells, allowing them to move faster and more efficiently absorb viruses and bacteria.
Fever-range temperatures promote the production of immune-related proteins, such as interferons, which are particularly important for early antiviral responses. These proteins help limit viral replication in neighboring cells and enhance immune surveillance.
Fever speeds up metabolic processes throughout the body. This increased metabolic rate can enhance the immune response by accelerating the production of antibodies and cytokines, and speeding up tissue repair. Elevated body temperature enhances the efficiency of neutrophils, immune cells that combat infections.
Understanding When to Act
While fever is a natural response, knowing when to seek medical attention is important. For adults, a temperature of 103°F (39.4°C) or higher warrants a call to a healthcare provider. Seek immediate medical attention if a fever is accompanied by severe symptoms like a stiff neck, a rash that does not blanch when pressed, unusual sensitivity to light, mental confusion, persistent vomiting, difficulty breathing, chest pain, or seizures.
In infants, fevers are a particular concern. If a baby younger than 3 months has a rectal temperature of 100.4°F (38°C) or higher, medical attention should be sought immediately, even if no other symptoms are present. For infants between 3 and 6 months old, a rectal temperature higher than 102°F (38.9°C), or a lower temperature accompanied by unusual irritability or sluggishness, should prompt a call to the doctor.
For comfort, fever-reducing medications like acetaminophen or ibuprofen can be considered. For mild fevers not causing significant discomfort, medication may not be necessary. Aspirin should not be given to children or teenagers due to the risk of Reye’s syndrome.
Supporting the body during a fever involves staying well-hydrated and getting sufficient rest. Drinking plenty of fluids like water, clear broths, or oral rehydration solutions is important to prevent dehydration, as fevers can lead to increased fluid loss. Rest conserves energy, allowing the body to focus its resources on fighting the infection. If you have any concerns or if symptoms worsen, always consult a healthcare professional.