Ah headache due to dehydration I can understand - I experience it when I'm using the AC for too long, especially in the car on a hot summer day.
Didn't realize heating air would reduce (relative) humidity and cause dehydartion too.
Thanks for the tip; will try keeping an open container of water to replenish the humidity, once I get my heater.
In car, I will try a wet cloth or something.
