Immunity to sickness (also known as sickness resistance) is a property that protects your character against both disease and food poisoning. When you have the immunity, you never need to use a unicorn horn or spell to cure sickness. In vanilla NetHack, this property is very rare: you must polymorph into a fungus or a ghoul to have immunity to sickness.
When you have immunity to sickness, you may safely eat old corpses (rotten or tainted), including corpses from mummies or zombies. This does not imply that a Necromancer or Undead Slayer may safely eat anything; among other problems, corpses can be acidic or poisonous.
Disease attacks of monsters like Juiblex do not affect characters with immunity to sickness.
- "You feel a slight illness."
- A monster used its disease attack against you, but you have immunity to sickness.
- "It doesn't seem at all sickening though..."
- Appears immediately after the "Ulch! That <food> was tainted!" message. The corpse would give you food poisoning, but you have immunity to sickness.
During enlightenment, the message for this property is, "You are immune to sickness."