"I'm always interested in causes behind symptoms that often get lumped in under "repetitive stress injuries" (RSI). We blame typing and poor ergonomics for a lot of our woes, but when I was having a lot of trouble with hand pain, it was a matter of changing my diet, not my desk configuration. Of course, it took a couple doctors before someone thought to have me tested for food allergies (first I had to suffer through the here-take-some-drugs-and-wear-wrist-splints phase followed by the let's-sign-you-up-for-expensive-physical-therapy-you-can't-afford phase). That's when I found out I was intolerant to gluten and dairy and that eliminating them helped tremendously.
If you're in the same boat where you've tried a lot of the common fixes for hand/wrist/joint pain etc. and haven't found them all that helpful, it's definitely worth trying to get to the bottom--figuring out what's causing the symptoms rather than just trying to treat them.
I was recently surfing around the web and found a list of the common symptoms of vitamin B12 deficiency. The fact that numbness/tingling in the hands was on the list, of course, caught my eye. Here's a list of some of the typical symptoms:
1. Itchy or tingling tongue. The tongue suddenly itches from time to time without warning. This occurs on the edge of the tongue, along one side or the other or at the tip. Some individuals experience stinging, pain, or tingling instead of itching.
2. White spots in the skin, resulting from melanin becoming absent in the area. These often occur on the outside of the forearm, but may occur in other places. The longer these spots are there, the whiter they get. As time goes by, the spots become very dry and flaky to the extent that small raw spots of skin may be exposed.
3. Sharp stabbing, tingling pain in the palm of one or both hands. This occurs suddenly and for no apparent reason in a spot directly below the ring finger, approximately where the first palm crease is. If B12 deficiency is not treated, a tingling pain may begin to occur along the outside edge of the hand, starting from the wrist. This pain occurs when the wrist is extended." (Continued via Ergoblog) [Usability Resources]