Many minor bumps to the head cause only a brief headache and bruise, but some head injuries cause bleeding or swelling inside the skull that can be dangerous. Go to the emergency room or call your local emergency number if, after a head injury, there is any loss of consciousness, repeated or forceful vomiting, a severe or steadily worsening headache, confusion, unusual drowsiness or difficulty staying awake, seizures, weakness or numbness, slurred speech, vision changes, or clear fluid or blood leaking from the nose or ears.
Extra caution is needed for older adults, young children, people taking blood-thinning medication, and anyone who was injured at high speed or fell from a height, as they are at higher risk of serious bleeding even after a seemingly minor knock.
If the injury was minor and the person is fully alert with no red flags, they can usually be watched at home, but they should not be left alone for the first day and should return for care if any warning sign develops.