Many Australian children in foster care have never had a Christmas present.

They have come from turbulent homes and are often traumatised, having suffered neglect, abuse or family violence.

"It's hard for some of us to imagine that they never have had something new," Sandie de Wolf, chief executive of children's charity Berry Street, said.

ABC Radio Melbourne has teamed up with Berry Street for this year's Giving Tree Appeal, encouraging people to buy a Christmas gift online via the charity's website for one of the thousands of Victorian children in foster care.

Berry Street's Julie Hill said giving a personalised gift to a child had an impact that extended well beyond Christmas Day.

To illustrate, Ms Hill told the story of a boy she worked with, who we will call Harry (not his real name).

Nought to 100 in two seconds

Ms Hill said that because of the circumstances as to why he had come into foster care, eight-year-old Harry was "fairly hypervigilant".

Hypervigilance is often a symptom of post-traumatic stress disorder (PTSD).

People who are hypervigilant are constantly on the lookout for threats and can easily become anxious or agitated.

Ms Hill said Harry would go "from nought to 100 in two seconds flat".

"We would have to do a lot of things to try and make him feel calm."

At the time, Berry Street had an office bongo drum which they encouraged Harry to play whenever he visited.

"Something that helps kids feel calm are activities that are rhythmic and repetitive," Ms Hill said.

Harry learnt to use the office drum to calm himself but he didn't have a drum to use at home.

"So for one of the Christmases that he was with us we bought him his own bongo drum, and probably a better looking one than the one that was in the office," Ms Hill said.

There are children in Australia who have never had a Christmas present. ( Pexels/Negative Space/CC0 )

With the bongo at home, Harry was able to drum whenever he needed to.

"Not only did he enjoy the drumming, and it was an age-appropriate, cool thing for him to do, but there was tremendous therapeutic value for him as well as for his foster carers," Ms Hill said.

"If things felt a bit dis-regulated at home, he was able to go off and start drumming."

Christmas therapy

Foster parents are volunteers and the small carers allowance they receive often doesn't stretch to special occasions such as Christmas.

"Resources can be really stretched in foster care," Ms Hill said.

Berry Street aims to distribute 10,000 targeted presents this Christmas.

By donating money towards a gift for a foster child you can make a huge difference to that child's life.

"When a child hasn't necessarily had a safe Christmas, it's incredibly therapeutic for them," Ms Hill said.