I read some decent reviews and decided to give Mavala STOP a go. It's formulated to work on children as young as three and it helps prevent thumb sucking too.
The idea is simple: a clear, fast drying nail varnish which looks harmless but tastes bitter when in contact with saliva. It's not advised for children under three as their taste buds are not fully developed and it might not have the desired effect, and you have to be very careful not to use your hands to eat soon after applying it.
You use it every two nights and it doesn't take too long for you to notice an improvement. It says it might weaken your nails, you can see below my little girl's longer but slightly peeled nails after a few days' use.
My daughter needed a week or so. It was a painful period but it worked: she hated it so much she cried when I painted her nails (naughty mummy!) but it was one of those moments when you think you are doing the best for your children. It also helped break her very unattractive nose-picking habit, which is a bonus.
I was impressed, now I want everyone to try it. I want my colleagues and relatives to see whether it works for them too, but I am keeping this tiny bottle handy just in case my daughter needs it again!