Friend says she has a constant severe headache everyday along with nausea and lightheadedness. after a full work up with her family doc, gastro, and neurologist everything was normal. said it all started after she had food poisoning. what could it be?

Migraine headaches are one sided, pulsatile/throbbing, last several hours up to a couple of days, and may be associated with nausea, vomiting, worsening pain with light/sound, and can come with an aura. Treatment includes over the counter pain relievers, caffeine, and prescriptions. Diagnosis is clinical and based on history. Work-up including head imaging is typically normal