Question: how long does it take for baking soda and lemon to lighten skin?
Answer: Mix some lemon juice with 1 teaspoon baking soda to get a paste. Apply to dark spots, and leave on for 3-4 minutes before washing your face. Do this every day, and you'll find that the baking soda exfoliates the top layer of skin, and the lemon juice gets to work on the dark patches.