Fever

Fever is a temporary rise in body temperature, usually caused by an infection. In adults, a temperature of 38°C (100.4°F) or higher is commonly considered a fever, although normal temperature varies from person to person and during the day. Fever itself is not a disease; it is a sign that the body is responding to a problem.

Viruses and bacteria are frequent causes, but fever may also occur after certain vaccinations, with inflammatory diseases, or, less commonly, with other medical conditions. Common accompanying symptoms include chills, sweating, headache, muscle aches, fatigue, loss of appetite, and feeling generally unwell. In children, fever can appear suddenly and may cause irritability or sleepiness.

Most fevers improve as the underlying illness resolves. Rest, drinking enough fluids, and wearing light clothing are often helpful. Medicines such as paracetamol (acetaminophen) or ibuprofen can reduce fever and relieve discomfort when they are appropriate for the person's age and health condition. Fever should not be treated with aspirin in children because of the risk of Reye syndrome.

Medical advice is important if a fever is very high, lasts several days, occurs in an infant younger than three months, or is accompanied by symptoms such as difficulty breathing, severe headache, stiff neck, confusion, persistent vomiting, dehydration, a widespread rash, or seizures. These signs may indicate a more serious illness that requires prompt medical evaluation.