2. Headache Symptoms - US News and World Report
Headaches that occur suddenly (acute-onset) are usually due to an illness, infection, cold, or fever.

3. Headache  (Trust Mark: Doctor-Reviewed)
A headache is pain or discomfort in the head, scalp, or neck. Serious causes of headaches are extremely rare. Most people with headaches can feel much better by making lifestyle changes, learning ways to relax, and occasionally by taking medicatio...• Reviewer: Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.