Treating your wooden cutting board with mineral oil can protect the cutting surface and keep it looking like new. The oil prevents the wood from drying, which can lead to warping and cracking, and it keeps water from settling in the small cuts and crevices on the board. You may find it odd to apply mineral oil to a surface that is used for food preparation, but rest assured that food-grade mineral oils are safe to use on cutting boards. In fact, many mineral oils are designed specifically for this purpose.
Purchase a mineral oil that is labeled as "food grade" or "food safe." These oils are commonly marketed as products specifically for butcher blocks or cutting boards, but they can also be found in the drugstore. See the Resources section for a few examples. Any other mineral oils are not approved for use on surfaces that come in contact with food.
Wash your cutting board with a sponge and gentle liquid dish soap. Rinse with warm water and dry thoroughly with a kitchen towel.
Pour a small amount of the mineral oil into a clean cloth and rub it over the surface of the cutting board. The exact amount of oil will depend on the size of the board, but you want to use enough oil to coat the entire surface liberally.
Let the board sit for at least three or four hours while the oil works its way into the wood. If you have time, let the board sit overnight.
Wipe the surface of the board with a clean cloth to remove any excess oil.
Rinse the board quickly under warm water and pat dry with a clean towel before you use the board for food preparation.
Oil your cutting board at least once a month. In the summer or in very dry climates, you may need to oil it every two or three weeks. Boards that are used and washed frequently may also need to be oiled more regularly.