Vomiting after a traumatic incident, especially a blow or jolt to the head, can occur with a concussion, but it may also signal a more serious brain injury such as intracranial bleeding or raised intracranial pressure.

Seek emergency care now if vomiting is repeated or accompanied by worsening headache, confusion, unusual behavior, increasing drowsiness, fainting, seizure, weakness/numbness, unequal pupils, poor coordination, or slurred speech. The CDC lists repeated vomiting as a danger sign requiring urgent assessment.

Even one episode warrants medical evaluation if the person is taking blood thinners, is older, was intoxicated, has a bleeding disorder, or the trauma was significant. Vomiting is specifically assessed after head injury, though it is less reliable alone than features such as post-traumatic amnesia. S Das A Manual on Clinical Surgery, p. 512.

Do not drive, play sports, drink alcohol, or stay alone after a suspected head injury. If you meant trauma without any head impact, tell me what happened and when the vomiting began.

Vomiting only after eating does not rule out a head-injury problem. It could be from food-related stomach upset, pain, stress, or concussion, but after trauma it still needs attention.

Go to an emergency department now if:

Repeated or significant nausea/vomiting after a head injury is a CDC danger sign. Do not assume it is merely the food. Until assessed, take small sips of water or oral rehydration fluid, avoid alcohol and heavy meals, do not drive, and have a responsible adult stay with you.

If there was no head injury and it was a single vomit after food with no severe pain or other symptoms, monitor closely and stay hydrated.