Headache Culprits

I've always been quick to blame headaches on staring at the computer monitor too long or tension in the upper back/shoulders from sitting all day, but for some people, it may just be a matter of not drinking enough water.  According to Signs of Dehydration, not getting enough water can cause headaches, fatigue, flushed skin, and several other maladies.  I'm still glad I bought the big LCD monitor (read: no glare) last year, though.