Playground crazes, like life, come at you pretty fast. At my daughter's school in the past few weeks, standing around waiting for the bell to go, I've noticed quite a few of the girls wearing large colourful bows in their hair. The first popped up like a poppy in a cornfield a few months ago; now there are dozens of these garish, oversized ribboned clips, and they are spreading like nits – only prettier and less hassle to get out of the hair. It turns out that they are '"JoJo bows", named after and copied from the teenage YouTube and reality TV star JoJo Siwa.

The 13-year-old dancer from Nebraska has a line of her signature bows for sale at Claire's Accessories, and pre-teens are going crazy for them. They have become so ubiquitous and big, that some schools have banned them for being too distracting. One mother has written on Mumsnet that her 10-year-old daughter spent all of her £100 Christmas money on the bows, which can cost as much as £12 each. I find it amazing that a parent could let her pre-teen child spend quite so much money on hair accessories, but this is what playground crazes do – they send children crazy.

These fads are, of course, nothing new: when I was 10, in the early 1980s, we all wore brightly coloured leg-warmers over our school socks to soften the clumpy edges of our Clarks shoes in an attempt to emulate the kids from the TV series Fame. But while that show made some of my schoolmates want to take up disco dancing like Coco or the cello like Julie, we never had these characters reach out from the screen into our homes in the way social media stars can to young children today. The old Fame stars have given way to the new celebrity, who talks to your child like a big sister or brother.

YouTubers like JoJo and Zoella, who earns more than £50,000 a month from her channel offering fashion and beauty tips to more than 10 million subscribers, bear a heavy responsibility for what they impart to young minds. As any parent knows, it can be difficult to correct a wildly inaccurate "fact" your child has heard in the playground. If they are told something from a social media star, seemingly endorsed by the viewing habits of millions of others, it is gospel: the challenge to correct it is magnified a million times.

JoJo Siwa
YouTube and reality TV star JoJo Siwa

Personally, I don't think these JoJo bows are ideal role model material for a young girl, but I'd be fairly relaxed about my six-year-old wearing one. Despite these hair clips screaming all the princessy stereotypes, JoJo says her bows are "more than just a hair accessory, it is a symbol of power, confidence, believing-ness", and I am all for that kind of message.

My daughter has, so far, never heard of JoJo Siwa, but her ability to navigate the internet scares me, and when she goes on to YouTube I watch her like a hawk. Gigantic bows and beauty tips are fairly innocuous, and Zoella has been rightly praised for giving a big sisterly confidence to young girls who might otherwise lack self-esteem at home. But their influence is so powerful, with the ability to mould young minds, parents need to monitor closely what their children are watching.

The Swedish YouTube star PewDiePie, who denied accusations of anti-Semitism last month after it emerged he had paid two viewers to hold up a sign reading: "Death to all Jews", was able to get away for months with showing swastikas and doing Nazi salutes (which he claimed was "humour") on his channel, which has 27 million subscribers. It was only after footage emerged of the two Indian viewers complained about the offensive sign did YouTube cancel his new series and drop him from their Google Preferred list, and Disney also severed ties with the controversial star. Until then, his videos were largely unmonitored.

That is a long way from Fame. If our children are free to watch the raw and unfettered content from YouTubers, it is up to parents to do the monitoring.

Jane Merrick is a freelance journalist and former political editor of The Independent on Sunday. She writes an allotment blog, Follow : @janemerrick23