It isn't throwing up, it is actually showing you that it dislikes that food you just gave it. It will cause the happy hearts to go down - make sure not to buy that food again for your tamagotchi :furawatchi:
it might not be barfing it could actually be yawning.Yawning happens when ur tama is about to go to sleep,just check if it is just yawning at night. <_<