Did you know that supermarkets often add a little-known “Julian date” to packs of fresh fruit and veg? These usually tell suppliers and stores when the produce was packed and are different from consumer-facing “best before” and “use by” dates. Some thought that a similar source of information might lie on the bottoms of our toothpaste packs, too. In 2024, for instance, a viral podcast clip suggested that the little patch may reveal whether the ingredients in the tube are “natural” or “chemical” (though that distinction is impossible to make). That misinformed claim has since been thoroughly debunked. But it leaves another question – what are the markers actually for, then? Why are there coloured squares on my toothpaste pack? According to dental health company Colgate, they’re used in the manufacturing process. When factories produce packs of toothpaste, they fill the tubes’ contents at speeds as fast as 200 containers a minute. Machines fill the opened cylinders with exact gram amounts of the product. Then, they need to be closed (usually by heat sealing) to …