Fever is a common physiological response to infection, inflammation, or certain medical conditions. It involves an elevation of body temperature above the normal range, typically around 98.6°F (37°C). Fever is a complex process regulated by the body’s thermostat, the hypothalamus, and is often a sign that the immune system is actively responding to an underlying threat.

Symptoms:

1. Elevated Body Temperature: The hallmark symptom of fever is an increase in body temperature. A fever is generally defined as a body temperature higher than 100.4°F (38°C).
2. Chills and Shivering: Many individuals with fever experience chills and shivering as the body tries to generate and conserve heat.
3. Headache: Fever can be accompanied by a headache, contributing to overall discomfort.
4. Muscle Aches: Generalized muscle aches and weakness are common during a fever.
5. Sweating: As the body temperature rises, sweating may occur as a cooling mechanism.

Causes:

1. Infections: Most fevers are a response to infections caused by bacteria, viruses, fungi, or parasites.
2. Inflammatory Conditions: Non-infectious inflammatory conditions, such as rheumatoid arthritis or inflammatory bowel diseases, can lead to fever.
3. Heat-related Illnesses: Exposure to extreme heat, leading to conditions like heatstroke, can cause fever.
4. Certain Medications: Some medications may induce fever as a side effect.
5. Autoimmune Disorders: Conditions where the immune system mistakenly attacks the body’s own tissues can result in fever.
6. Cancer: Certain cancers, particularly blood cancers like leukemia, can cause fever.

Types:

1. Low-Grade Fever: Body temperature slightly above the normal range, usually up to 100.4°F (38°C).
2. Moderate Fever: Body temperature ranging from 100.4°F (38°C) to 102.2°F (39°C).
3. High Fever: Body temperature exceeding 102.2°F (39°C).
4. Intermittent Fever: Fever that comes and goes at regular intervals.
5. Remittent Fever: Continuous fever with fluctuations exceeding 2°F (1.1°C) but remaining above normal.
6. Pel-Ebstein Fever: A specific type of fever pattern seen in some cases of Hodgkin’s lymphoma, characterized by fever spikes lasting several days followed by afebrile periods.

While fever itself is generally not harmful and often indicates the body’s defense mechanisms in action, persistent or high fevers may warrant medical attention. Seeking medical advice is crucial, especially if fever is accompanied by severe symptoms, lasts for an extended period, or occurs in vulnerable populations such as young children or the elderly.