It was on a family holiday that Kali Kushner discovered, abruptly, just how others viewed her skin. “At the end of the day I washed off my makeup,” she recalls. “My nephew said: ‘Why is your face so dirty?’ It took me a minute to realise he saw my foundation as a ‘clean face’ and acne as dirt.”

Soon after, Kushner, 23, from Cincinnati, Ohio, began documenting her struggle with acne on the Instagram account @myfacestory – her experience with the drug Accutane, dermarolling, makeup, scarring, hyperpigmentation, alongside all the ways people have responded to her acne, from her husband, who has been steadfastly supportive, to the traffic police officer who assumed she was a junkie. To her surprise, people began following. Today, with more than 50,000 followers, she makes up part of the growing acne positivity movement.

After years of oppressive aesthetic perfection, acne positivity is a drive for people to be more open about their skin problems, from the occasional spot to full-blown cystic acne. It joins recent moves to celebrate the many and varied appearances of our skin – from vitiligo to freckles and stretch marks – but also seeks to educate those who still believe that acne is a problem for the unwashed and unhealthy.

Blogger Em Ford, who posted the 2015 YouTube video You Look Disgusting showing her acne. Photograph: David M. Benett/Dave Benett/Getty Images for AllBright

Many trace the movement back to the British blogger Em Ford, who in 2015 posted a YouTube video called You Look Disgusting. It showed her both in full makeup and bare-faced with her acne visible, as a succession of comments people had posted about her skin sprung up around her: “WTF is wrong with her face?”, “I can’t even look at her”, “Ewww, gross, horrible, ugly …”. In the first week alone, it amassed 10 million views. Ford, whose YouTube channel My Pale Skin now has more than one million subscribers, will shortly launch You Look Disgusting 2.0.

Others have followed, including the Colorado Instagrammer Hailey Wait and the British beauty blogger Kadeeja Khan, as well as a host of celebrities – from Kylie Jenner promoting her favourite spot treatment to Justin Bieber’s Instagram post that claimed “Pimples are in” and Lorde’s sardonic replies to people giving her unsolicited skincare advice. Last year, Teen Vogue launched the inaugural Acne awards.

Kushner developed acne in high school. “Whiteheads, blackheads, the usual stuff.” It was around the age of 20 that she developed adult cystic acne. “It was hard. And extremely painful. I had no idea what was going with my skin. Nothing worked. Or if it did, it didn’t for long.”

She grew increasingly socially anxious, certain that everyone she met was staring at her skin. “One time I remember I was talking to my friend in class and started laughing at a joke she told me. As I was laughing, a cyst burst open and started bleeding down my face. It was horrifyingly embarrassing. I ran out of the classroom and didn’t come back for the next two weeks.”

Dr Bav Shergill of the British Association of Dermatologists says that acne “often affects people without much power in society, such as adolescents”. He tells of a US study in which participants were shown a selection of photographs of high-school students with skin problems, as well as photographs of the same students with their acne airbrushed out, and asked for their impressions. The results, Shergill says, showed that “as soon as you have any disfigurement on your face, you get viewed as an introverted nerd”.

‘Pimples are in’: Justin Bieber. Photograph: Matt Baron/REX/Shutterstock

While many regard acne as a teenage affliction, it can evolve into adulthood. An estimated 25% of all women over 30 still have the condition. “I see so many women – adult, professional, intelligent women – who have had their lives ruined by acne,” says Shergill. Women often find that their breakouts are tethered to the hormonal shifts associated with their menstrual cycles. “Female hormonal acne is miserable,” Shergill says. “You may not get many spots a month, but each one will leave a scar. And every scar has both an emotional and a physical component.”

Corrinne, an educational psychologist from Folkestone, turned 40 in August. To celebrate, she visited the Mac Cosmetics counter for a makeover. Sitting before the makeup artist, she felt horribly, painfully exposed. “I couldn’t make eye contact,” she says. “To sit there with my face naked, I felt so vulnerable.”

Every morning, Corrinne dedicates an hour to the process of getting ready, with the bulk of that time set aside for makeup. She will use a base, foundation, concealer, then more foundation, then powder, then a spray to fix it. It is not an attempt to look unfailingly glamorous: “I’m just trying to get myself to a baseline to face the world.”

It has been like this since she was 14. At school, she would wear makeup so thick it was “almost a mask”. She hated to be seen in daylight and would use a tiny vanity mirror rather than something that showed her whole face or full length. She spent an hour and a half getting ready for school each morning, and at lunchtime she would go home to reapply her foundation. At breaktimes, she would head straight to the toilets to check her concealer. Comments were made that she says shaped her. “I remember someone said I’d put so much make-up on, it looked like Polyfilla.

“Without social media, it was isolating, lonely, secretive. I thought I was acne. I thought I wasn’t bigger than that.”

In her 20s, she met a friend who had also suffered from severe acne. To find someone who understood so fully, who would discuss it openly and felt no shame, was hugely helpful to Corrinne – it was a taste, perhaps, of today’s acne positive attitude. “I wish we’d had that movement when I was 14,” she says. “I think it’s a fantastic thing.”

When Kushner began her Instagram account in 2015, it was solely for herself – a private page to track her progress on Accutane. “I wasn’t really interested in sharing my journey at first because I didn’t realise that others were going through the same thing,” she explains. “I wanted to document my skin and side-effects so that I could look back on it and see how far I’ve come.”

When she made her page public, it was an act of defiance. “If anything, my account was a rebellion against the typical beauty blogger accounts at the time,” she says. “There was no curation taking place, no filters, angles, and certainly no Photoshop. I would take out my phone, take a picture, think of a caption within four or five minutes and post it. It was and always has been about keeping it real. It was a call against stereotypical standards of beauty, saying that you don’t need X/Y/Z to be beautiful. All you need is you.”

I looked at my friends who didn’t wear makeup and I realised when they had pimples they still looked beautiful

This attitude has now spread to other previously flawless areas of social media. Jessica Olie is a fitness guru known for her Let’s Start Yoga ebook and an Instagram account in which she is often photographed holding yoga poses in charming locations around the globe. A year or so ago, Olie’s account broke its carefully calibrated perfection in favour of a new kind of honesty, documenting her divorce, her father’s illness and her problems with her skin.

Olie suffered from teenage acne, exacerbated by the constant exposure to chlorine as a competitive swimmer, and in her late teens was prescribed the pill. Five months after she stopped taking the contraceptive last year, her skin went “haywire” – worse, she says, than when she was a teenager.

For someone who makes a living out of looking enviably, radiantly healthy, posting honestly about her skin problems came with a degree of risk. “If someone said: ‘You’re supposed to be healthy, why is your skin bad?’, I’d tell them just because you’re healthy it doesn’t mean your skin is good, and just because your skin is good it doesn’t mean you’re healthy.”

And the pursuit of perfection can be wearisome. “I think I was fed up of not feeling pretty or beautiful enough because I had a few pimples. I looked at my friends who didn’t wear makeup and I realised when they had pimples they still looked beautiful.” Today, she posts pictures and videos of herself makeup-free, her skin mid-flare or masked by splodges of spot cream. “People put you on a pedestal, they think everything in your life is perfect, so it’s nice when people on social media reveal there are things they don’t feel confident about.”

The niceness seems to be spreading. Last year, the photographer and activist Peter DeVito was surprised to find the supermodel Cara Delevingne had reposted a picture of the words “Acne is normal” emblazoned across his acne-marked face. He had recently come to the conclusion that “it was dumb to retouch an image [on social media] for hours, just to post it where people would forget about it in minutes”. These days, he says: “It makes me happy when people accept themselves for the way they look and learn to stop comparing themselves to other people on social media all the time.”

Kushner, too, has felt a shift in attitudes. “Honestly, there hasn’t been as much backlash as you would think,” she says. “At first, definitely. People will always have something negative to say no matter what you do or post or say, so that’s important to keep in mind. But now I feel like our little community has been able to educate those who were once ignorant on the subject. It feels like a more understanding and accepting place than it was four years ago. I only hope that it continues to grow and the community continues to shine its light.”