Mild soaps such as liquid dish detergent mixed with water work well for cleaning butcher block. You also can use a solution of bleach and water to help prevent bacteria. Just combine 1 tablespoon bleach with 1 gallon of water. This works really great if you keep the solution in a spray bottle; just spray and wipe the wood after each use. One thing you should never use on wood countertops is a scouring cleanser like Comet.
Wood countertops intended for use as cutting surfaces are finished with penetrating oil, usually mineral oil of some type. In order to maintain this finish and keep the wood stain-resistant, you should periodically apply non-toxic oil, once every few months. USP-grade mineral oil is the best; it is the cheapest food-grade oil and it is available at your local drug store. Vegetable or olive oil should not be used; it will turn rancid.
Warm the oil up a little prior to applying with a soft cloth, wiping along the grain direction. Let the oil to soak in for four to six hours then wipe off any excess oil that didn’t soak in.
What about all those spills and marks seemingly branded into the wood? How do you get rid of stains on older butcher-block countertops? You could go ahead have the surface sanded and resealed. But before you do, give this a try: shake some salt over the marks, and then scrub the wood with the cut open side of a lemon half. Letting the wood sit overnight, rinse with water afterwards. For the darker stains, sponge on a solution of 3 percent hydrogen peroxide and water.
If you do decide to sand and reseal, consider using one of the professional alternatives to mineral oils. You can find wood sealers designed for food surfaces at many woodworking supply outlets. Look for products called Salad Bowl Finish; these are approved as non-toxic for food contact on countertops and cutting boards and require less frequent maintenance. Enjoy your clean new countertops.