Fever Causes: Why Your Temperature Rises and What to Do

Introduction A fever, medically known as pyrexia, is characterized by a temporary increase in the body's internal temperature. While the average body temperature is often cited as 98.6°F (37°C), it is normal for individuals to experience slight fluctuations throughout the day. A fever is generally considered to be a temperature of 100.4°F (38°C) or higher. It is important to understand that a fever itself is not a disease; rather, it is a physiological response—a signal from the body’s immune system that something unusual is occurring internally. When the body detects a threat, such as a virus or bacterium, the hypothalamus—the part of the brain that acts as a thermostat—may reset the body to a higher temperature. This elevated heat is thought to help the immune system function more efficiently while making the environment less hospitable for invading pathogens. While a fever can cause significant discomfort, it often plays a vital role in the body's defensive strategy. However, persistent or extremely high temperatures may require professional medical evaluation to determine the underlying trigger. Common Causes The most frequent triggers for an elevated body temperature are related to the body's response to external pathogens. These may include: Viral Infections: Conditions such as the common cold, influenza (the flu), and COVID-19 are among the most frequent causes of fever. These viruses trigger an immune response as the body attempts to neutralize the infection. Bacterial Infections: Bacterial pathogens can cause localized or systemic fevers. Common examples include strep throat, urinary tract infections (UTIs), and bacterial pneumonia. Gastroenteritis: Often referred to as the "stomach flu," this inflammation of the digestive tract—caused by viruses, bacteria, or parasites—may lead to fever alongside digestive distress. Ear Infections: Particularly common in children, infections of the middle ear (otitis media) can cause sudden spikes in temperature. Skin Infections: Conditions like cellulitis, where bacteria enter the deeper layers of the skin, may result in redness, warmth, and a systemic fever. Immunizations: It is common for children and adults to develop a low-grade fever after receiving vaccines. This indicates that the immune system is learning to recognize and fight a specific pathogen. Heat Exhaustion: Prolonged exposure to high temperatures or intense physical activity in the heat can overwhelm the body's cooling mechanisms, leading to an elevated core temperature. Less Common Causes While infections are the primary culprit, other underlying issues may cause the body's thermostat to rise: Autoimmune and Inflammatory Disorders: Conditions such as rheumatoid arthritis, lupus, or inflammatory bowel disease (IBD) may cause the body to attack its own tissues, leading to chronic or intermittent fever. Malignancies: Some forms of cancer, particularly leukemia and lymphoma, are sometimes associated with persistent or unexplained fevers, often occurring at night. Blood Clots: Deep vein thrombosis (DVT) or a pulmonary embolism may trigger an inflammatory response that includes a low-grade fever. Certain Medications: Some individuals may experience "drug fever," a reaction to specific antibiotics, anti-seizure medications, or blood pressure drugs. Associated Symptoms Depending on the underlying cause, a fever rarely appears in isolation. Individuals may experience a variety of accompanying signs that help healthcare providers narrow down the diagnosis. Common associated symptoms include: Chills and Shivering: As the body attempts to reach the new, higher temperature set by the hypothalamus, a person may feel cold despite having a warm forehead. Sweating: When the fever "breaks" or begins to come down, the body releases heat through perspiration. Headache and Muscle Aches: Systemic inflammation often leads to generalized body aches and tension headaches. Dehydration: Higher temperatures cause the body to lose fluids more q