I grew up in Colorado and have an idea for you. First of all, and I'm sure you know this, what you describe is not altitude sickness. The only pure headache's I saw from folks coming from the east, had more to do with the bright sun than the altitude. Good sunglasses, hat and sunscreen usually cured the ailment.
Altitude sickness is a whole other beast that I have witnessed; ruined an elk hunt in the Weminuche (sp?) wilderness when my partner started throwing up had terrible headache and dizziness. Getting to lower altitude is the only solution once Altitude sickness sets in. There are ways to lower a persons risk for this ailment if started a week before heading into the high country (+10k ft).
If some is good and more is better, then too much is just right.
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