Out of all the things your teenagers can do, getting themselves punched with holes isn't the worst. But it's still scary. You wonder where it will stop.
My 16-year-old wants both ears studded with jewellery. I should count myself lucky, I suppose, that she's not thinking of piercing her tongue.
It's the same with tattoos. I know the Beckhams have got them. Angelina Jolie has a dozen, I think. But they still make me very uneasy. What if you change your mind? And don't tattoos look horrible when you get old and your skin goes all wrinkly?
Piercings leave a scar. Tattoos remind you forever of the day you got inked.
What it boils down to, I think, is that I don't want my teenagers doing anything they'll regret, whether it's piercings, tattoos, unexpected babies or mind-rotting drugs. Most things you can put right with money and time. But why make life hard for yourself?
'What if you have a tattoo,' I say to my eldest, 'and then you want to get the kind of job that disapproves of them?'
'Like what?' he says.
Fleetingly, I imagine Kate Middleton with blue barbed wire round her neck.
'I don't know,' I say. 'A lawyer. An accountant. Someone who works in an office making a lot of money.'
I live in hope.
'You wear a shirt in an office,' he says. 'No one would see.'
This is the problem with arguing with teenagers. They're wise to the arguments before you've even said them.
When I was 18, my boyfriend's mother fainted when she saw he'd got an earring. (It was a long time ago.)
I don't want to be like that. But I think if any of my offspring end up branded like sheep, I might faint, too.