Children are whitening their skin with make-up to avoid being bullied or racially abused at school, according to charity NSPCC.
Its research suggested racial abuse and bullying of children had risen by one-fifth since 2015-16.
There were over 10,500 race hate crime offences against children across the UK in 2017-18 - an average of 29 a day.
A 10-year-old girl told NSPCC she "tried to make her face whiter" as others described her skin as "dirty".
The girl who called Childline to discuss her distress said: "My friends won't hang out with me anymore because people started asking why they were friends with someone who had dirty skin.
"I was born in the UK but bullies tell me to go back to my own country. I don't understand because I'm from the UK.
"I've tried to make my face whiter before using make up so that I can fit in. I just want to enjoy going to school."
'Gets me down'
An 11-year-old Asian child also told the helpline that she tried to change the way she looked by using eyeliner.
"I'm being bullied at school because I'm Chinese. The other kids say that my skin is yellow, call me names, and it gets me really down," she said.
"I've tried to change the way that I look by using eyeliner so that I fit in more. I don't want to tell my parents because I think it would upset them."
While a 16-year-old girl from a Muslim background said: "People call me a terrorist and keep telling me to go back to where I came from.
"I dress in traditional Muslim clothes and I think it singles me out.
"I usually just put my head down and get on with it but it's getting to the point now where I genuinely feel like I might get attacked."
Research by the NSPCC suggested the number of hate crime offences recorded by police against under-18s went from 8,683 in 2015-16 to 9,752 in 2016-17.
The figure then rose to 10,571 in 2017-18.
The charity requested data from all UK police forces under the Freedom of Information Act, receiving figures from 38 out of 45.
Girls were more likely to contact Childline and the most common age group was between 12 and 15, the research found.
Head of Childline John Cameron said: "Childhood bullying of this nature can cause long-term emotional harm to children and can create further divisions in our society.
"If we see a child bullying another because of their race we need to tackle it head on, by explaining that it's not OK and how hurtful it is."
Police chiefs have raised concerns over the heated public debate around Brexit and the "febrile" atmosphere that it has created.
The UK's head of counter-terrorism policing, Neil Basu, said in January that a spike in hate crime seen around the 2016 EU referendum had "never really receded".
Police figures for all hate crime showed sharp rises around the time of the 2016 EU referendum and the 2017 terror attacks in London and Manchester.
Levels decreased again until early 2018, when they again began to rise.