Almost everybody gets a headache from time to time. It may be a tightness around the temples or a stiff neck after staring at a computer screen all day. It might be face pain from a sinus infection or after snorting up too much pollen on a lovely spring day. Tension is the most common trigger of headaches, but missing sleep, skipping meals or drinking alcohol can lead to them, too. These factors, and others, can contribute to your headaches. But what is actually causing the pain?