I hope it's not carpal tunnel.
It's probably tendinitis/RSI. Carpal tunnel from typing is much, much less common than the media might have you believe.
David, just in case you haven't heard this before, the three keys to curing tendinitis are (1) frequent rest breaks, (2) posture/ergonomics, and (3) keeping your body healthy. When typing became painful for me, it took me a few tries before I found a doctor who knew what to tell me. The GPs I saw were useless. It wasn't until I saw a doctor that specialized in occupational injuries that I was given good advice. The specialist I saw (Dr. David Diamond, Head of Medicine at MIT; sees hundreds of RSI patients/year) said that my injury wasn't yet serious (even though I was experiencing semi-regular hand/wrist pain), and that there were some simple things I could do to alleviate the tendinitis (the three keys above).
He recommends a 30 second break every 5 minutes---stop typing, stand up, walk around, roll your shoulders, move your arms. The longer you type without a break, the greater the chance of serious injury.
Evaluate your ergonomics. When you type, your feet should be flat on the floor, your back should be straight, and your keyboard should be low and close to your body. If there is any tilt to your keyboard, it should be slightly negative (away from the body). Most of the products sold as ergonomic aids (e.g. wrist rests) aren't helpful, though your mileage might vary (YMMV). When not typing, don't lay your hands/wrists on the keyboard/desk, lay them in your lap.
Last, but not least, keep your body healthy. Eat a variety of foods & exercise regularly. The better you take care of your body the better it can heal any damage done by typing.
If the pain doesn't go away, get yourself to an occupational injury specialist who has experience with RSI patients. Hope you're feeling better!
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