“Sometimes,” the TikTok star known as “Cucumber Guy” intones at the start of his videos, “you need to eat an entire cucumber.”

Then, he starts to slice.

The influencer, Logan Moffitt, has set off a worldwide wave of chopping, pickling, and crunching by sharing viral recipes for cucumber salads prepared in a plastic deli container.

In Iceland, the virtual craze has created a real-world problem: A nationwide cucumber shortage.

Daniel Sigthorsson, 30, who lives in Reykjavik, the capital, wanted to try a salad of his own. But there were no cucumbers in his local grocery store, he said. And there were none in the second shop he visited, he said. Or the third.

“I was like, ‘That’s weird,’” he said, laughing. “That’s one of the things we never run out of in Iceland. And then I saw the news.”

Icelandic news reports blamed the social media craze for the challenges that home cooks like Mr. Sigthorsson have encountered obtaining cucumbers. The ingredient has gone missing from stores across the Nordic country, according to interviews with shoppers and tour guides, as well as data shared by Kronan, one of Iceland’s biggest grocery chains.

Kronan said cucumbers have sold out in stores across Iceland. The sales picked up so quickly that the store did not have time to prepare, said Gudrun Adalsteinsdottir, the company’s chief executive.