A Spider Eye is a food item added in Beta 1.9 Pre-Release 2. It is dropped by both spiders and cave spiders when killed by the player, but is not dropped when one has died from environmental damage (such as a mob grinder or trap). It can be eaten by the player, but it will poison the player for four seconds, causing damage.
Spider Eyes can also be made into potions when added to a waterbottle (into a brewing stand). It will make a Mundane Potion, the other is a Potion of Poison creating when mixing it with an Awkward Potion.
Despite the fact that the Spider Eye is poisonous and can be consumed to slightly replenish hunger, it will only harm a player's health instead of just the player's hunger.
It could even be used when one's health bar is down to a few hearts, because poison cannot kill the player (it does not reduce health below ).
Although Spider Eyes can only produce negative effects for potions, they can be used as an attack when made into a Splash Potion (brewing Gunpowder into a potion will make it a Splash Potion).
Spider Eyes exist in the Xbox 360 edition of Minecraft.
As of Minecraft 1.9 Prerelease 3, if a Spider Eye is mixed into a Awkward Potion it will create a Poison Potion. A Poison Potion hurts the player for a set amount of time, just like getting attacked by a Cave Spider.