evidence: The toothpaste theory claims that the small coloured square at the bottom of a toothpaste tube indicates its ingredients. Experts reveal if this theory is true. [...] Multiple social media posts claim that the tiny square you see on the bottom of the tube of your toothpaste is actually part of a colour code related to the ingredients present in the product. [...] To figure out what ingredients are present in your toothpaste, you can check the ingredient list printed on the packaging. Moreover, the front or sides of the toothpaste packaging often highlight key features such as 'whitening', 'fluoride', 'sensitive', etc. These labels give you clues about specific ingredients or benefits the toothpaste offers.