When Penny’s owner Ben Hertz added an activated charcoal latte to the coffee shop’s lineup, it instantly became a most-Instagrammed item.

And it’s no wonder: the drink’s milky swirls, in perfect shades of millennial gray, were entrancing.

But a few months later, he added something else to the menu: a disclaimer.

Activated charcoal binds to other drugs which can make them less effective, it read. Please only drink 2 hours before or 1 hour after taking medications.

His message reflects the latest concerns about a novel ingredient that has quickly become both trendy and controversial.

Charcoal becomes “activated” when it is heated and combined with gas or another agent, expanding its surface area. Its primary use is as a toxin remover — to help with drug overdoses or poisonings. But it started cropping up in the food and beverage scene a few years ago as a “health” additive; a natural detox. Now, as some proclaim it a super substance that can cure a hangover, whiten teeth and ward off aging — not to mention turn foods jet black — it’s showing up in everything from lemonade to ice cream.

“We sell more and more of it,” says Hertz, who recently added a charcoal soft serve. “Everyone wants it. And they want it in everything.”

Cocktail consulting company Bittercube recently debuted a black slushee, complete with edible glitter, on the cocktail menu at Can Can Wonderland.

“We use it to create a black backdrop,” says Bittercube boss Nick Kosevich. “It just makes for a visually stunning cocktail.”

A little goes a long way; Kosevich uses about a 16th of a teaspoon in each cocktail, which he says isn’t enough to harm anyone.

But some still worry that even small amounts could nullify medications — including birth control, according to studies — for unknowing consumers.

“There are people who don’t know how to use it properly, and if you have it in too high a dose it can be problematic,” says Robb Jones, the bar director at Spoon and Stable and Bellecour. “People need to think about where they’re getting it from, and how much you trust the people who are making it.”

Come on, try it!

Curious?  Taste these three charcoal drinks: 

Activated charcoal latte

Penny’s, pennys.com

Sip this foamy gray beauty with or without espresso; don’t forget the photo. (The location on 44th St. also has charcoal soft serve.)

Charcoal lemonade

Truce, drinktruce.com

It may be as black as night, but with a hint of sweetness and lots of tart lemons, it’s every bit as refreshing as the original.

Star Stuff

Can Can Wonderland, cancan wonderland.com

This vodka cocktail is paparazzi-worthy, complete with disco dust, gold luster and prosecco twinkling from inside a slushee machine.