The active ingredient is miraculin, a glycoprotein in the pulp. It binds to the sweet taste receptor on your tongue without activating it, so nothing happens at first. When acid lowers the pH in your mouth, the protein changes shape and turns the receptor on, which is why sour foods suddenly register as intensely sweet. Nothing about the food changes: the lemon is still as acidic as it was, your reading of it is what has been altered. The effect typically runs about thirty minutes to an hour, sometimes longer, and it fades as saliva washes the protein away. Eating something salty or fatty tends to shorten it.

The berry itself is unremarkable as a food and grades clean on almost every trigger column we track. The reason it is not on supermarket shelves as a sweetener is regulatory rather than toxicological. In the 1970s a company was set to launch miraculin commercially, and the FDA classified it as a food additive rather than treating it as generally recognised as safe, which meant a long and expensive approval path the venture did not survive. The berries and freeze dried tablets are sold as food today. The genuine safety question is not the berry but the behaviour it enables, since a session tends to involve eating far more acid than anyone normally would.

The berry grades B for histamine, a mild mark, and A for nickel, sulfites and free glutamates, so it is not itself a concern. The problem is indirect and worth taking seriously. Flavour tripping is built around citrus and vinegar, and lemon and lime both grade D as histamine liberators, meaning they prompt your body to release its own histamine. Sourness is normally what limits how much of them you eat, and miraculin removes that limit. If histamine is your trigger, either skip the session or plan what you will taste in advance and keep it away from citrus and vinegar.