Rotten Flesh

Rotten Flesh is an item from the 1.8 update dropped from zombies. It will poison the player, but restore some of the hunger meter. As of the pre-release testing, poisoning causes no damage by itself. It is unclear whether poisoning causes creatures to do increased damage to the player or not (EDIT: As of the 1.8 Leak, the poison effect causes a player to take half as much damage. It is unclear if this is a bug or an intended effect).

Rotted flesh heals Wolves without poisoning or causing damage to them. This can be useful because you won't have to heal by wasting your food and giving them something that has nothing of use to you.