A few days ago I was taking a tour of Corcovado National Park in Costa Rica and I noticed that my hearing was muffled. I don’t hear that well normally, but this felt like I was wearing earplugs. That sometimes happens when I fly, and I just yawn to make my ears pop and the problem goes away.
That didn’t work this time. My ears stayed muffled through the whole day out. But after the tour and the long boat ride back, they finally popped and my hearing came back to normal during the drive back to my hotel.
What happened? I was severely dehydrated during the tour (the tour operator did not bring nearly enough water for such a hot day) and I picked up several liters of bottled water on the drive home. Just as I was finishing the first liter, my ears popped and my hearing came back. I searched for information on this condition and found a lot of pages saying that heavy exercise can cause it and cooling down will make your ears pop again. But I had several hours sitting on the boat after the exercise and my ears did not pop until I got a lot of water in me. I’m certain that this was caused by dehydration.
I had something similar happen at work a few months ago, and I now think it was also due to dehydration. My doctor had me nearly eliminate caffeinated and carbonated drinks and I hadn’t yet got used to making up for it with a lot more water. Looking back, I think the dehydration affected my Eustachian tubes. Clearly, I have to pay more attention to getting enough to drink.
Charles Engelke's Blog 