# Poison
Poison is one of the most annoying hazards of the early game for any player who has not yet gained immunity to it.
There are many ways in which a NetHack character will come into contact with poison.  Some monsters wield poisoned weapons or fire poisoned arrows, while others such as killer bees have a poisonous sting or bite.[1]  Poison is also used in many of the traps in the dungeons.  Finally, certain kinds of corpses are poisonous, and cause 1 to 15 HP and 1 to 4 strength loss when eaten,[2] but never instadeath, though the HP loss may be enough to kill a player with low health.
Poisoning from eating a poisonous corpse is different from food poisoning, which is a type of sickness.

Contents

1 Effects
2 Statistics
3 Poisonous corpses
4 Strategy

4.1 Poison resistance
4.2 Avoiding poison
4.3 Treating attribute loss
4.4 Poisoning weapons

5 Food poisoning versus poisonous corpses
6 Variants

6.1 SLASH’EM
6.2 UnNetHack
6.3 FIQHack

7 References

Effects
The effects of poison are:

HP loss.
Loss of attribute points, especially strength but also dexterity and constitution.  A potion of sickness can reduce any of your attributes.
Small probability of an instadeath, depending on the type of poison exposure. This probability is per exposure, not per source.

The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Per commit d0b11fd2, poison no longer has a chance of instakilling the player.  Instead of the instakill, the player suffers 6+4d6 damage, half that of max maximum HP loss, and loss of attribute points.
Statistics

Source
Chance of poison
Chance of deadly
Chance of stat damage

Monster melee attack
1 in 8 successful attacks that pass your magic cancellation
1 in 30 poison attacks
1 in 6 poison attacks will damage either strength, dexterity or constitution depending on the monster.

Monster ranged attack
?
1 in 30 successful attacks with a poisoned thrown weapon[3]
1 in 2 chance of damaging strength

Poisoned dart trap
1 in 6
1 in 10 hits
1 in 2 chance of damaging constitution

Poisoned spiked pit
1 in 6
1 in 8 falls
5 in 8 chance of damaging strength

Noxious gas container trap
depends on luck
1 in 15 chance
1 in 3 chance of damaging strength

Poisoned needle container trap
depends on luck
1 in 10 chance
1 in 2 chance of damaging constitution

Poison blast attack from an iron golem or green dragon
?
1 in 15 chance
1 in 3 chance of damaging dexterity

Poisonous corpse
4 in 5
none
always damages strength, deals d15 HP damage

Poisonous corpses
The following monsters leave poisonous corpses:

all k
all a except giant ants and fire ants
all S except garter snakes and pythons
all werecreatures
gremlins
manes, homunculi, lemures
rabid rats
giant spiders, scorpions
xans
vampire bats
(baby) green dragons
yellow molds
adult guardian nagas
quantum mechanics
Medusa
jellyfish
salamanders
the Chromatic Dragon
Scorpius
Note that a corpse being poisonous is independent of its monster having poison resistance and/or granting poison resistance when eaten.

Strategy
Poison resistance
The best way to protect yourself from poison is to obtain poison resistance as soon as possible.  Intrinsic poison resistance is granted by eating any of a large variety of corpses (listed in Dylan's Dragon Resistances spoiler).  Most, but not all, of these corpses are poisonous themselves, so it is not advisable to eat them without some way of avoiding or curing the strength loss.  It can be avoided by wearing an external source of poison resistance (e.g. an amulet versus poison) or a ring of sustain ability, and it can be cured by applying a unicorn horn. Tinning the corpse is another option; the tinned meat will no longer be poisonous but will still convey the intrinsic.
Several roles start with poison resistance or gain it at an early level.  Barbarians and Healers have starting poison immunity, as do orcs.  Monks gain it at level 3.

Avoiding poison
There are other precautions you can take to protect against specific encounters with poison:

High magic cancellation protects against poisonous bites and stings but not poisoned weapons.
Unless you know that you can fix the stat loss, don't drink unidentified potions that could be a non-blessed potion of sickness.
Don't try to untrap dart traps until you have poison resistance.
If a random scroll you read turns out to be stinking cloud, discharge it harmlessly by choosing to center the cloud a long way away from you.
Learn what corpses are poisonous, and don't eat them until you have poison resistance.
Treating attribute loss
Repeated exposure to poison at the beginning of the game is likely to reduce your strength and carrying capacity, thus limiting the weight of your inventory. You want to find a noncursed unicorn horn and apply it repeatedly to regain strength.  When you see the message "This makes you feel great!", all your stats have been fully restored.
Potions and spells of restore ability can restore lost attributes, but a unicorn horn is the best solution. You can also pray: being overtaxed with at least four points of strength drain is considered major trouble, and having any reduced attributes at all is considered minor trouble.

The following information pertains to an upcoming version (NetHack 3.7.0). If this version is now released, please verify that it is still accurate, then update the page to incorporate this information.

Unicorn horns can no longer restore strength.
Poisoning weapons
You can hurl poisonous missiles yourself. Poisoned weapons do an additional d6 damage and have a 10% chance of instadeath against non-poison resistant foes.
Missiles become poisoned if dipped into a potion of sickness—arrows of any kind, as well as crossbow bolts, darts, and shuriken may be poisoned this way.[4]
However, lawful gods do not approve of poisoned weapons, and will exact a small alignment penalty from followers who use them.

Food poisoning versus poisonous corpses
Differences between food poisoning and poisoning from poisonous corpses:

Food poisoning comes from corpses that have become "tainted" from age (this includes the corpses of zombies and mummies), while poisonous corpses are toxic from the moment they hit the ground.
Eating a poisonous corpse has an immediate, not necessarily lethal effect, while food poisoning causes sickness that will kill you after a few turns, unless you are able to cure it in time.
A poisonous corpse will give the message "Ecch - that must have been poisonous!", while food poisoning is indicated by "Ulch - that meat was tainted!   You feel deathly sick."
Poison resistance protects against the effects of eating poisonous corpses.  Only sickness resistance protects against food poisoning.
Food poisoning can be avoided by eating only fresh corpses.  The other type of poisoning can be avoided by learning which corpses are inherently poisonous.
It is possible for a corpse to be both poisonous and tainted.  A rotting kobold corpse fits both criteria, as does the corpse left by a kobold zombie or mummy.

Variants
SLASH’EM
In SLASH'EM, you can also poison weapons by dipping them in a toilet.

UnNetHack
In UnNetHack, the chance of an instadeath from poison is replaced with a "very toxic" poison that damages max HP and does strength damage, reducing the chance or frustrating YASD (though it is still nearly always fatal to low level characters). Other detriments of being poisoned remain the same.

FIQHack
FIQHack also eliminates poison instadeath and replaces it with permanent attribute damage, which cannot be fixed via potion or unicorn horn. Additionally, poison resistance only halves poison damage, ensuring that it is never completely safe to eat a poisonous corpse; chances of attribute reduction are also lowered to one third of the time, and the attribute loss itself is reduced by a third.
Since poison resistance only partially protects you in FIQHack, the amulet versus poison and the ring of poison resistance are even more useful as they completely protect you from the effects of poison.

References

↑ poisoned in Attrib.c

↑ src/eat.c in NetHack 3.6.0, line 1583

↑ src/attrib.c in NetHack 3.6.0, line 258

↑ include/obj.h in NetHack 3.6.0, line 200

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