Hemoptysis

Hemoptysis is an unlockable passive item added in The Binding of Isaac: Repentance.

Effects[]

Double-tapping a fire button causes Isaac to sneeze blood, dealing damage to enemies in front of him. The sneeze deals damage equal to 1.5x Isaac's damage, knocking enemies and projectiles back. Enemies knocked back take 10 damage when hitting a wall or obstacle and deal 10 damage to other enemies they hit.
- The sneeze has a cooldown of 1 second.
The sneeze applies a curse to enemies. Enemies under the curse will take more damage from Brimstone-like laser attacks and violently explode on dying to these attacks, damaging and spreading the curse to nearby enemies. Any enemies spawned by those under the curse will also be cursed.
- The following attacks will deal increased damage (2x damage +3):
  - Brimstone attacks from Azazel/ Tainted Azazel
  - Athame
  - Brimstone
  - Brimstone Bombs
  - Lil Abaddon
  - Lil Brimstone
  - Maw of the Void
  - Montezuma's Revenge's brimstone (not tears)
  - Mega Blast
  - Shoop Da Whoop!
  - Trisagion
- However, the Brimstone ball from The Forgotten/ Tainted Forgotten with Brimstone does not get the damage bonus.

Tainted Azazel begins with an inherent version of Hemoptysis that allows him to deal full damage to cursed enemies.
The sneeze's range is affected by the shot speed stat, and not by the range stat itself.
The sneeze can push Bombs, pickups and enemy shots.
The collision damage can be used to damage Hosts while their skulls are lowered.

Azazel / / Brimstone / Lil Brimstone / Trisagion / Montezuma's Revenge/ Mega Blast / Brimstone Bombs / Maw of the Void / Lil Abaddon / Athame / Shoop Da Whoop!: Damage dealt by Brimstone or Brimstone-like beams is increased on targets that have been sneezed on. The vulnerability is indicated by a brimstone indicator.
Fire Mind: The sneeze will still set enemies on fire, but not cause explosions, similar to its interaction with Brimstone.
Loki's Horns: Chance to sneeze in all cardinal directions.
Lost Contact: The sneeze reflects enemy shots.
Monstro's Lung: Multiple sneezes are applied around the character.
The Wiz: Shoots two sneezes diagonally instead of one straight forward.

Ipecac: The sneeze causes an explosion. The explosion deals additional damage equal to 3x Isaac's damage +10 and will not hurt Isaac.
Tainted Azazel: The innate sneeze ability is entirely separate from Hemoptysis, and so the sneeze can be triggered twice in quick succession. However, triggering the sneeze from Hemoptysis will cancel Tainted Azazel's brimstone charge, meaning that this item is largely ineffective as this character.