What causes a fever?

When the immune system detects an infection, it can reset the body’s internal thermostat, producing warmth, chills, sweating, tiredness, or aches. Respiratory infections such as a common cold, acute bronchitis, bronchiolitis, COVID-19, or croup may cause fever alongside cough or breathing symptoms. Skin infections such as cellulitis, and illnesses such as chickenpox or brucellosis, can also present with fever. Fever can have non-infectious causes too, including a medicine reaction, inflammatory disease, or overheating. The pattern of symptoms matters more than the temperature alone.

Rest, drink fluids regularly, and wear light clothing in a comfortable room. Measure temperature with a reliable thermometer and record the reading, time, and associated symptoms. Use paracetamol or another suitable medicine only according to the label or a clinician’s advice, especially for children or people with liver, kidney, stomach, or pregnancy concerns. Avoid cold baths and do not combine products that contain the same ingredient. Antibiotics do not treat viral infections unless a clinician identifies a bacterial reason.

Get urgent help for trouble breathing, blue or grey lips, confusion, a seizure, severe dehydration, a stiff neck, a rapidly spreading rash, or difficulty waking. Seek prompt assessment for a very young infant with fever, a weakened immune system, serious long-term illness, or a fever that is persistent or worsening. Medical review is also sensible when the cause is unclear or symptoms are interfering with drinking, urination, or normal activity.

Ask which cause best fits the symptoms, whether testing is needed, how to manage temperature safely, and which warning signs should change the plan. Share recent travel, sick contacts, new medicines, and the timing of any rash, cough, pain, or urinary symptoms.