I have heard about this before but could never duplicate the problem. Laptops run on 12 to 19 volts DC. Laptop Keyboards are made of plastic and silicone which are very good insulators. But there may be a small possibility that your power source (electrical outlet) may not be grounded properly. Or your AC adapter doesn't have that 3rd prong (direct ground) or you are using one of those 3 to 2 wire adapters.
I guess this only occurs when it is plugged in? I also guess this doesn't happen when running on just the battery?
I would HIGHLY suggest to replace your AC adapter before it kills your laptop.
Also I know this may have something to do with high water content in your body. And may be you could try another one such as Toshiba Laptop Keyboard.