What is pain restricted to one side of the head?

Migraine?: One-sided headaches are often migraines. Other, more serious problems can also be implicated. Any new headache symptoms (especially one-sided) needs to be worked up by a doctor. A headache journal can be helpful in this. Consult a neurologist. http://www.headaches.org/for_professionals/headache_diary.

Possible migraine: Head pain especially on one side of the head can be migraine pain. There is usually throbbing, sensitivity to light and/or sound, nausea or vomiting. Sometimes funny sensations, tastes, or visual changes precede the pain. These symptoms are called an aura. Other causes: infections in ears, sinuses, mastoid. Shingles are chickenpox that return on one side. Pain often occurs before the rash appears.

Could be migraine. : Severe unilateral headache is often due to migraine or cluster-type headache. Typical symptom include sensitivity to light, sound or smells. Nausea and eye pain are also common. Most people will feel tenderness at the upper trapezius or base of the neck. Pain can be triggered by stress fatigue or dehydration and can last from a few hours to a few days. See a doctor to talk about meds.