Cough syncope causes: what can trigger fainting

A bout of coughing raises pressure inside the chest. This can temporarily reduce the amount of blood returning to the heart and lower blood flow reaching the brain. A person may feel light-headed, have blurred vision, lose awareness briefly or slump and recover quickly. The cough itself may arise from an airway illness, reflux or another problem, so the fainting episode should be considered separately from the cough.

Contributors that make light-headedness more likely include not drinking enough, low blood glucose, anaemia or an irregular heartbeat. Read about [Dehydration](/conditions/dehydration/), [Anaemia](/conditions/anaemia/), [Hypoglycaemia](/conditions/hypoglycaemia/) and [Atrial Fibrillation](/conditions/atrial-fibrillation/) if these have been mentioned in your care.

Sit or lie down as soon as warning symptoms begin, preferably with your legs supported. Do not drive, climb, swim alone or use machinery until a clinician has reviewed an unexplained blackout. Note what happened before the cough, how long awareness was lost, any injury, and whether there was chest discomfort, racing heartbeat or confusion afterwards. Keep hydrated unless a clinician has given you a fluid restriction, and arrange an assessment to identify the cough and check for contributors.

Seek emergency help if fainting occurs during exertion, causes a serious injury, happens with chest pain, severe breathlessness, a sustained irregular heartbeat, blue lips, a seizure-like episode or prolonged confusion. Urgent assessment is also needed for repeated blackouts, a first unexplained faint, or fainting while sitting or lying down. Do not assume coughing is the only cause when these warning signs are present.

Could my cough, medicines, hydration, blood count or heart rhythm be contributing? Do I need an ECG or other tests? What activities should I avoid until the cause is clearer? How can I reduce coughing safely?