When your child bites their fingernails it can be really tricky to help them stop.
Simply asking them not to do it anymore doesn't work and foul tasting deterrents are not always effective.
Paediatric psychologist Amanda Abel said nail biting or onychophagia was a common childhood behaviour often learned from parents.
"Nail biting is often passed down from parents – children with nail biters for parents are almost three times as likely to bite their own nails," Ms Abel said.
"It's most commonly seen in children aged between 3 and 6, and is prevalent in typically developing children as well as those with developmental or emotional challenges."
And while in most cases nail biting won't cause children serious harm, there can be some negative outcomes.
"Mild nail biting rarely causes any issues other than social embarrassment and minor cosmetic changes in the hands," she said.
"More severe nail biting can cause disfigurement of the nail, bacterial infections and oral health issues."
However, once a child has formed a regular habit it's important parents tread carefully when addressing the issue so as not to cause distress.
"Parents should be careful how they discuss and address this behaviour as punishing it can lead to decreased self-esteem for their child and has even been shown to increase the nail biting," she said.
"Parents should be aware that most children will 'grow out' of nail biting, so just monitoring it and perhaps encouraging activities that prevent the behaviour (such as drawing or engaging in other activities using the hands) will help parents feel like they're doing something productive without focusing on it as a specific problem."
Why children bite their nails is still largely unanswered, and there are many different opinions. While some people claim nail biting is a result of anxiety, nervousness and boredom, others are not so sure that's the case.
"People often think that nail biting is a result of anxiety, or a frustration release behaviour. However, research is still inconclusive about this and there's been little research to back up this claim," she said.
"However, we do know that children are more likely to bite their nails when they're alone or watching television."
She recommended parents use distraction techniques (like playing outside), offer up replacement behaviour options (like drawing) or provide alternative objects to chew, to help their child stop biting their nails.
Dr Anne Malatt said anxiousness lead to her biting her nails when she was a child.
"I used to bite my nails ferociously as a child and young adult," Dr Malatt said.
"I did not stop until middle age and even now have been known to have a nibble or two under certain circumstances, even though I now have healthy and beautiful nails that I love to take care of."
Despite trying everything, she struggled to stop. When she started dealing with her anxiety through a variety of ways, including breathing techniques, she got her nail biting under control.
She suggested parents' talk with their child and teach them some strategies to manage their anxiety, like gently breathing through the nose.
"The only thing that has helped me has been learning to deal with my underlying anxiousness – being honest about the fact that it is there, why it is there, and learning to take steps to deal with it," she said.
"Nail biting is a symptom of anxiety, and therefore a great marker of how we are actually feeling.
"I think that if kids are biting their nails, that is a great marker for them and for their parents that something is going on for them and all is not well, and a great opportunity to talk to them about what is going on."