Why are they so dangerous?

The companies that make the packets use different formulas, but one thing is clear: They contain more than just soap, said Dr. Diane Calello, the medical director of the New Jersey Poison Information and Education System at the Rutgers New Jersey Medical School.

Highly concentrated detergent and a variety of chemicals are inside, depending on the brand, she said. Tide pods contain 90 percent active ingredients and 10 percent water, according to the company. A dissolvable covering holds it all in.

“What we’ve seen is when children or adults bite into these things that moisture-sensitive membranes basically just disintegrates and the contents explode inside your mouth,” she said in a phone interview.

That’s when the pain sets in. The chemicals cause severe burns to the mouth, esophagus or respiratory tract, she said, adding that some very young and very old patients with cognitive issues have been rushed to emergency rooms or even died as a result of eating the packets.

“This is not something I would put anywhere near someone’s mouth,” she said.

How did this even start?

The origins and inspiration of the challenge are murky, but jokes have circulated online about the temptation of a product that is known to be dangerous but that bears a resemblance to brightly colored candy.

In late 2015, the satirical publication The Onion published commentary from a child’s perspective in which he vowed to consume one.

“From the very second I saw those blue and red detergent pods come out of that shopping bag last week, I knew immediately that, come hell or high water, I would eat one of those things,” he wrote.