my daughter had a pimple on her forehead about 5 months ago but she still has a scar. is mederma worth buying or going to work?

Mederma may help the scar appear softer, but it will not remove it completely. It's worth a try though. If it doesn't work, try using an over-the-counter skin lightening cream containing kojic acid or hydroquinone on the effected area. This should gradually fade the acne scar.