If you don't want to keep a separate cutting board for garlic and onions, you can deodorize a cutting board by rubbing it with salt.

To reduce the smell of garlic from your hands, rub them with salt and lemon juice. If gadgets attract you, you can buy a stainless steel bar that you rub over your hands to eliminate the odor. It's said to break the ion bonds, releasing the odoriferous allium compounds from the skin, although cooks' opinions vary as to its effectiveness. Using the bowl of a stainless steel spoon or even a stainless steel faucet in a kitchen sink also may work. Then wash your hands well with soap and hot water.