The box claims the candy is infused with 9 million-Scoville-unit chili extract, referring to a measure of spiciness. The famously hot Ghost pepper is rated at around 1 million Scoville units.

So where a habanero might top out around 300,000 Scoville heat units — a measurement for spiciness — bear spray is more like 2 million. On the skin, it feels like terrible sunburn.

One hundred years ago, an American pharmacist named Wilbur Scoville developed a scale to measure the intensity of a pepper’s burn. The scale – as you can see on the widely used chart to the ...