What causes a fever?

Your immune system may raise body temperature as it responds to germs. Respiratory infections such as the common cold, acute bronchitis, COVID-19, croup, or bronchiolitis can do this. Skin and other infections, including cellulitis, may also cause fever. Chickenpox and brucellosis are additional examples of conditions that can include a raised temperature. The temperature alone cannot identify the cause, and a fever may occur with or without obvious local symptoms.

Rest, drink fluids regularly, and choose light clothing unless you are shivering. Check your temperature with the same method when monitoring it, and note other symptoms such as cough, rash, pain, vomiting, or urinary changes. Fever-reducing medicine may help discomfort when used exactly as directed for your age and health; do not combine products that contain the same ingredient. Avoid strenuous activity and alcohol while you feel unwell. A clinician can help identify the source when fever persists, returns, or is accompanied by worsening symptoms.

Seek urgent help for confusion, difficulty breathing, a seizure, a severe headache with a stiff neck, fainting, blue or grey lips, or a rapidly spreading rash. Prompt assessment is also wise for a very young baby with fever, an older adult who becomes suddenly unwell, or anyone with a weakened immune system. Arrange medical advice if you cannot keep fluids down, are passing very little urine, or the fever is not settling and your overall condition is deteriorating.

Ask what cause best fits your symptoms, whether you need an examination or tests, which fever medicine is suitable with your existing conditions, and what changes should prompt reassessment.