they're probably not bad, but you can get the one's which make you look really orange. You have to be so careful with the creams that you can't see the bronzer/tan because when you wake up your face will be orange or not blended in properly. Oh, and remember to wash your hands!
It's pretty much harmless, but remember to make it even. And next time you go on holiday go for a tanning session

Natural tans are so much more attractive than the fake stuff!
Good luck!