A friend of mine received a call at midnight from the daughter she thought was on a sedate sleepover with a group of other 15-year-olds.
'Hi, Mum,' said a tired voice. 'We're at the hospital.'
Someone had brought a bottle of vodka. One of the girls was having her stomach pumped.
There aren't many things that are good for you in small quantities, but poisonous if you have too much. Deadly nightshade, chocolate, weedkiller - you know where you are most of the time. But alcohol is weird. You can't say to your teenager, don't ever touch it, because you know, somewhere at the back of your mind, that it has the odd health benefit. As well as potentially leading to cirrhosis of the liver.
As if that weren't confusing enough, you also know that anything you forbid completely becomes, in that instant, much more desirable.
So you try to explain the dangers instead. Don't drink too young (because your brain's still growing), don't drink on an empty stomach (because it'll make you sick), don't drink too much (ditto).
'What do you count as too much?' says my eldest.
If only it were a bit more like smoking: don't ever do it, you'll get hooked, it'll kill you. Here it's all shades of grey, a thick fog of units and moderation.
Also, I have noticed, it's very hard preaching the evils of drink with a glass of wine in your hand.