as Kelly says they dont bite unintentionally I have had guinea pigs for over 25 years and only have i ever been bitten bad once and that was my fault for putting my hand between a naughty boy after a female still got the scar ( my guinea pig trophy scar lol) but if they bite its more of a nibble its quite sweet they are not vicious animals by nature and would rather run, so relaly you have nothing to be worried about they are sweeties, my one golden rule with my kids has always been never ever put your hand between 2 pigs especailly if they are arguing and none of my kids have ever been bitten, try not to worry about them biting you as your nervousness could affect the way they bond with you, alwasy talk to them so they know your voice, as i open my 2 sheds every morning no matter how I am feeling i greet them all hello my beautiful little girls/boys and the greeting I get back makes my day, I'm sure the other girls know what I mean, ;D