There was an urban legend that Mikey, the kid from the Life cereal ads who won't eat anything, ate Pop Rocks and washed them down with a cola, and then died when his stomach exploded. It's completely untrue. If you swallow a handful of Pop Rocks and chug a cola, you'll probably burp, but you won't die. If Mikey barely tried Life cereal, why would he eat Pop Rocks anyway?
Pop Rocks are made by mixing sugar, lactose, corn syrup, water, and artificial colors/flavors. The solution is heated until the water boils off and combined with carbon dioxide gas at about 600 pounds per square inch (psi). When the pressure is released, the candy shatters into small pieces, each containing bubbles of pressurized gas. If you examine the candy with a magnifying glass, you can see the tiny bubbles of trapped carbon dioxide.
When you put Pop Rocks in your mouth, your saliva dissolves the candy, allowing the pressurized carbon dioxide to escape. It's the popping of the pressurized bubbles that makes the sizzling sound and shoots pieces of candy around in your mouth.
Are Pop Rocks Dangerous?
The amount of carbon dioxide released by a packet of Pop Rocks is about 1/10th as much as you would get in a mouthful of cola. Except for the carbon dioxide, the ingredients are the same as those of any hard candy. The popping of the bubbles is dramatic, but you won't shoot candy into your lungs or chip a tooth or anything. They are completely safe, though I doubt the artificial colors and flavors are particularly good for you.