‘Blackheads are like snowflakes,” says Dr Sandra Lee. “No two are the same. That’s what makes them beautiful.” In 2014, the Californian dermatologist joined Instagram. Among the usual SoCal posts – juice, sand, selfies – she uploaded a 15-second video of her extracting a blackhead. She noticed a surge in followers, so she did it again. The same thing. “I knew people might be interested, but it turned out there was a whole subculture of people who loved popping videos. A subculture that is still growing.”

Dr Lee – or Dr Pimple Popper, as she has playfully rebranded herself – has 2.1 million followers. She has become a social media celebrity and launched her own acne cream. Her fans are, she says, mostly women between 18 and 35, often people who can’t afford to see a dermatologist in real life and want to learn. “A generation ago, people used Yellow Pages to find dermatologists. This way, they can connect with you before you’ve met.” Her clients now travel from Alaska, London and Saudi Arabia.

Her fans, called popaholics, are roughly divided into soft popaholics and hard popaholics. Is it a bit like porn, then? “That’s your reference,” she says, “but, essentially, soft pops are blackheads and whiteheads. Something simple, with no blood. Hard pops are what people graduate to. Cysts, rhinophyma [on the nose], things like that.”

The process is mundane, punctilious and disgusting. Using a comedone extractor, a silver stick with a looped head, she presses against the skin around the pimple and pulls back, squeezing out a strand of off-white discharge. It sounds gross because it is, but it’s also oddly fascinating. There’s an entire Subreddit devoted to voyeurs. “People watch them to relax, to go to sleep, to help with anxiety. It’s like a cleansing thing. I think there is a hypnotic quality, a little sense of euphoria. But I do think there is a feelgood side, too, watching someone being helped.” It’s a bit like watching Jaws for the first time, I say. “Yes, it’s that feeling of the unknown, of not knowing what’s going to come out.” Sometimes, in the case of abcesses, it’s horrific. “I don’t understand that,” she says, “although I didn’t like watching them, either. I’d describe myself as a born-again popaholic.”

The videos on Instagram are short. Longer ones end up on YouTube, where she also has an educational channel. Sometimes the videos are soundtracked with songs such as Duke Ellington’s Just Squeeze Me (But Please Don’t Tease Me) and French Montana’s Pop That. Her patients sign a waiver form consenting to being filmed, “but 99% of my clients say yes. People also want me to film.”

Such is the strength of the commuity of popaholics that one transatlantic couple “solidified” their relationship through watching her videos. When they got married, Dr Pimple Popper sent them a wedding gift. “It wasn’t the acne cream, no.”