What is a fever?
A fever is a temporary increase in body temperature above the normal range. Normal body temperature is around 37°C (98.6°F), though it varies a little between individuals and through the day, and a temperature of 38°C (100.4°F) or above is generally considered a fever. Rather than being an illness itself, a fever is usually a sign that the body is responding to something, most often an infection.
Fever is part of the body's natural defence. When fighting an infection, the body raises its temperature, which helps the immune system work and makes the environment less hospitable to some germs. This is why fever is often a normal and even helpful part of recovering from common illnesses. Most fevers, particularly those from everyday infections like colds, flu and other viruses, are not dangerous and settle as the underlying illness improves.
Common causes
Fevers have many possible causes, the vast majority of them infections that the body clears on its own. Common causes include:
- •Viral infections, such as colds, flu and COVID-19
- •Bacterial infections, such as throat, chest, ear or urinary infections
- •Common childhood illnesses
- •After some vaccinations, usually briefly
- •Heat exhaustion or being overheated
- •Less commonly, inflammatory conditions or other causes, particularly with prolonged fever
How to bring a fever down and care for one
Most fevers can be managed comfortably at home, and the aim is to help the person feel better while the body fights the underlying illness. The key measures are rest and drinking plenty of fluids to avoid dehydration, which is especially important as fever increases fluid loss. Keeping cool and comfortable — wearing light clothing and keeping the room at a comfortable temperature — helps too.
Paracetamol or ibuprofen, used as directed and appropriate for age, can reduce fever and ease the discomfort, aches and headache that often come with it. They are not always necessary if the person is otherwise comfortable, as the fever itself is helping fight the infection, but they are useful when someone feels unwell. It is best to avoid cold baths or sponging to bring a fever down quickly, as this can be uncomfortable and counterproductive. The main focus is comfort and hydration while watching for warning signs.
Fever in children
Fever is very common in children and is usually caused by minor viral infections that clear up on their own. In most cases, how a child looks and behaves overall matters more than the exact temperature reading — a child who is alert, drinking and reasonably comfortable is generally reassuring, even with a fever. The priority is keeping them comfortable and well hydrated, offering fluids regularly.
Paracetamol or ibuprofen, in the correct dose for the child's age and weight, can be given if the child is distressed or uncomfortable, though they are not always needed simply to bring a number down. There is no need to undress a child completely or sponge them with cool water. Encouraging fluids and watching how they are overall is the main approach.
Certain situations need prompt medical attention. Always seek urgent advice for a fever in a baby under three months, for a child who is very unwell, drowsy, difficult to wake, or has a rash that does not fade when pressed, or who has difficulty breathing or a fit (febrile convulsion). For older babies and children, seek advice if a fever is very high, persists beyond a few days, or the child seems to be getting worse. When in doubt with a child's fever, it is always better to seek advice.
When a fever needs attention
While most fevers are harmless and settle on their own, some situations warrant medical attention. A fever that is very high, lasts longer than about three days, or keeps returning is worth getting checked, as is a fever accompanied by other concerning symptoms. The overall picture — how unwell the person feels and what other symptoms are present — matters as much as the temperature itself.
Certain warning signs need urgent attention: a stiff neck, a rash that does not fade when a glass is pressed against it, severe headache, difficulty breathing, confusion or unusual drowsiness, a fit, or signs of dehydration. In babies, older adults, and people with weakened immune systems, fevers warrant more caution and a lower threshold for seeking help, as infections can be more serious in these groups.
For most people, though, a fever is simply a sign that the body is doing its job fighting a common, self-limiting infection. Knowing both the reassuring norm — comfort, fluids and rest while it passes — and the warning signs that need help allows a calm, informed response to one of the most common symptoms of all.