Sweating, headache, nausea and fatigue

These symptoms can occur when fluid and salt losses affect circulation, especially after heat exposure, vomiting, diarrhoea or strenuous activity. A common cold, COVID-19, allergic rhinitis or chronic sinusitis may cause headache and tiredness alongside nausea or sweating. Dengue fever can cause a significant illness with headache, and heat exhaustion can worsen quickly if cooling and fluids are delayed. Generalised anxiety disorder may produce sweating, nausea, muscle tension and fatigue, but new or intense symptoms should not automatically be attributed to anxiety.

Stop strenuous activity, move somewhere cool and rest. Sip water or an oral rehydration drink if you can keep fluids down, and avoid alcohol. Note the onset, temperature, recent heat exposure, fluid intake, medicines, travel and any rash or breathing symptoms. Arrange medical advice if symptoms persist, recur, or interfere with eating, drinking or normal activity. Avoid anti-inflammatory medicines until a clinician has considered dengue if you have travelled to an area where it occurs or have a compatible illness.

Seek emergency help for a sudden worst-ever headache, fainting, confusion, seizure, stiff neck, weakness or numbness on one side, trouble speaking, chest pain, severe breathing difficulty, repeated vomiting or inability to drink. Urgent assessment is also needed for severe heat illness, unusual drowsiness or a rapidly worsening condition.

Ask whether you need checks for dehydration, infection, blood pressure or another cause of headache. Share travel history, heat exposure, fluid intake, new medicines, nasal symptoms, anxiety symptoms and whether the headache began suddenly or gradually.