When a patient has a severe headache, it causes sympathetic nerve stimulation and increased excitability of the sympathetic nerve. The sympathetic nerve mainly controls the gastrointestinal tract, and when the sympathetic nerve is excited, symptoms such as nausea, vomiting, and cold sweats will occur. There are many common diseases that cause headache with nausea and vomiting. When the intracranial pressure is increased, the sympathetic nerve is stimulated and the patient will also experience dizziness, nausea, vomiting, and headache. Severe migraines can stimulate the vomiting center, which can also cause patients to react with vomiting. There are also systemic diseases such as flu or fever when there is acute gastroenteritis, which may also cause headache due to fever, as gastroenteritis causes patients to have vomiting symptoms. If the vomiting is jet-like, it may be a sign of increased intracranial pressure.