What should you know about unilateral headache?

One-sided head pain can occur with migraine, which may include nausea or sensitivity to light and sound. Nasal blockage, facial pressure or a recent cold can point toward an upper-airway cause such as allergic rhinitis, chronic sinusitis or the common cold. Dehydration and heat exhaustion may bring headache with thirst, weakness, dizziness or heavy sweating. Anxiety can contribute to muscle tension and a tight feeling. A headache with fever needs context: viral illness, COVID-19 and dengue fever are among the possibilities in the right setting. A symptom pattern is not a diagnosis by itself.

Rest in a cool, quiet place, drink fluids steadily if you can, and eat if you have missed meals. Note the start time, side, triggers, severity, visual symptoms, nausea and any medicine taken. Use only pain relief that is suitable for you and follow its label; frequent use can itself sustain headaches. Arrange a clinical review when headaches recur, change pattern, interfere with daily activity or do not settle as expected.

Seek emergency care for a sudden, severe headache, new weakness or numbness, trouble speaking, confusion, seizure, fainting, stiff neck, repeated vomiting or new vision loss. Fever with a severe headache, a headache after a significant head injury, or symptoms during pregnancy also deserve urgent medical advice. Do not drive yourself if you feel confused, faint or unable to see clearly.

Does my pattern fit migraine or another cause? Which symptoms make this urgent? Could heat, fluid loss, congestion or a medicine be contributing? What headache diary details would help with diagnosis?