Pressed by parents to pose in videos with make-up and skincare products, pre-teen girls dubbed "Sephora Kids" have taken TikTok by storm in a trend that some specialists brand a danger to children's mental and physical health.

American girls between the ages of eight and 12 are gaining thousands of followers on the video platform by modelling their make-up purchases.

The trend focuses particularly on products from the French high-street brand Sephora, championed by reality TV star Kim Kardashian's daughter, North West.

Gushing over pots of moisturiser or begging their parents to buy them anti-wrinkle cream, they pose in front of the mirror with their hair tied back, aping popular grown-up make-up tutorials.

Skin specialists warned that some of the products used in the kids' videos contain ingredients not suited to young skin, such as retinol.

"Many of the 'skin influencers' sometimes are more trusted than real physicians," US dermatologist Danilo Del Campo told AFP.

"This has led to an increase in consultations related to skin reactions and concerns resulting from the misuse of these products," he warned.

"Most parents do not realise there are any risks."

Parroting famous beauty influencers, the "Sephora kids" review products from high-end lines, such as moisturisers costing nearly 70 euros ($76).

"How can these little girls spend like, my salary, really, in skincare?" said one Sephora salesperson in the United States, in a TikTok video.

- 'Self-esteem issues' -

Del Campo warned young skin can be damaged by unsuitable ingredients.

He has also seen "self-esteem issues" among his child patients who "feel the need to correct perceived flaws that may not actually exist."

Employees at Sephora have complained about the behaviour of young customers in stores with videos showing make-up counters in disarray with spilt products.

Sephora, which is part of the LVMH luxury group, did not respond to requests to comment from AFP.

Michael Stora, a psychoanalyst specialising in online behaviour, said the girls in the videos are "not playing with dolls as you might expect at their age -- they are the dolls."

Some mothers in the videos defend the trend as just a "game" -- but Stora accused parents of the "fetishisation" of their offspring.

Solene Delecourt, a professor at the University of California, Berkeley who specialises in social inequality, also believes the videos can "contribute to a very stereotypical representation of girls and women online".

"These are not women but little girls, and they are already subject to this intense social pressure," she said.

Delecourt released a study in the Nature journal this month which said that online images amplify gender bias, particularly against women.

And in recent months, TikTok and other social media platforms have come under fire over the impact of videos on young people.

In January, tech giants faced a grilling before the US Senate Judiciary Committee after being accused of not doing enough to thwart online dangers for children, including sexual predators and teen suicide.