It is highly alkaline and will raise the pH of the wood to a point where you cannot rinse it out. The higher pH will cause any stain or paint to fail prematurely, leaving you with a huge mess. There are cleaners available that will clean with an oxygenated bleach (instead of chlorinated) and will not ruin the wood. Wood ReNew from Perma-Chink is the best I've ever used. If someone has used bleach on your wood, you can reduce the pH and make the wood suitable for staining or painting again by applying oxalic acid to the wood.