If you don't want to try this way or are allergic to strawberries, activated charcoal makes a great natural tooth whitener too. (wellnessmama.com)
and baking soda as a highly effective and natural teeth whitener. (wellnessmama.com)
Lemon juice, lemon or orange peels, and apple cider vinegar are all items I've seen people tout as miracle all - natural teeth whiteners. (mindbodygreen.com)