"Fizzy" and "sour" get used almost interchangeably, but they're doing two completely different things to your mouth.
Sour is just acid
Sourness is a direct taste response — your tongue has receptors that detect acidity, and the more acid, the stronger the sour signal. Citric acid, malic acid and similar compounds coated onto a sweet trigger this directly, with nothing else happening chemically. It's a taste, full stop, and it lasts roughly as long as the acid stays in contact with your tongue.
Fizzy is a reaction, not a taste
Fizz is mechanically different. It needs two things in the same coating: an acid (typically citric acid) and a base (typically sodium bicarbonate — the same compound as baking soda). Dry, sitting on the sweet, they don't react. The moment saliva dissolves them, the acid and base react with each other and release carbon dioxide gas as a byproduct — tiny bubbles forming directly on your tongue. That's the sensation, and it's the same basic chemistry as a vinegar-and-baking-soda volcano from a school science lesson, just scaled down and flavoured.
Why the two get confused
Most fizzy sweet coatings include both citric acid and sodium bicarbonate, so you get the acid taste and the gas reaction at the same time — sour and fizzy together. But they're separable: a sweet can be heavily sour with no bicarbonate at all and never fizz, while a sweet with a lighter acid load but a good dose of bicarbonate can fizz noticeably while tasting only mildly sour.
Why it fades in seconds
The reactive coating is a thin dusting on the outside of the sweet, not the whole thing. Once saliva has worked through that layer and the acid-bicarbonate reaction has finished, the gas-producing reaction is over — there's nothing left to react. What's left underneath is usually a plain gummy or chew with none of the fizz, which is why the sensation front-loads hard in the first few seconds and then disappears completely.
Where to find it
Our Fizzy Sweets collection covers this properly, including the Kingsway range of fizzy tongue painters and fizzy fruit shapes, which pair the citric acid-and-bicarbonate reaction with a colour-changing effect for good measure.
Frequently asked questions
What makes sweets fizzy?
A reaction between citric acid and sodium bicarbonate coated on the sweet, triggered by saliva, which releases carbon dioxide gas.
Is fizzy the same as sour?
No — sour is a direct taste response to acid, while fizzy requires an acid-base reaction that produces gas. A sweet can be one without the other.
Why does the fizz disappear so fast?
The reactive coating is only a thin outer layer. Once it's dissolved and reacted, there's nothing left to fizz, even though the sweet underneath is still being eaten.