Certain spider enemies no longer target or deal contact damage to Isaac, nor actively spawn other enemies. Spiders that are spawned from enemies that are not affected by Bursting Sack will also remain neutral.
Affected spider enemies that deal no damage to Isaac whatsoever include: Spider, Big Spider, Swarm Spider, Strider, Rock Spider, Tinted Rock Spider, Level 2 Spider, Trite, Baby Long Legs, Small Baby Long Legs, Crazy Long Legs and Small Crazy Long Legs.
Spiders and Big Spiders don't blink red when Isaac has the item.
Swarm Spiders don't blink yellow when Isaac has the item.
Trites will still uselessly try to target Isaac.
Affected enemies that deal no contact damage but can still damage Isaac through other methods include: Ragling, Rag Man's Ragling, Blister, Ticking Spider, Migraine, Wall Creep, Blind Creep, Rage Creep, Soy Creep and The Thing.
Except for Ticking Spiders, Migraines and Wall Creeps, all other spiders will still uselessly try to target Isaac for contact damage.
Coal Spiders aren't aggressive to Isaac, but will still deal contact damage.
Twitchy is the only "spider" enemy that is still aggressive to and will still damage Isaac, as it's classified as a Gaper rather than a spider.