Poison can be inflicted by enemies such as snakes or the Arachnid!!!!.
This status ailment can be inflicted by the PK β.
Poison in EarthBound causes around 20 damage every turn in combat, and will occasionally cause damage while walking around outside of combat; each time this happens, the screen will blink red. It can be cured with PSI Healing β, Refreshing herb, Cup of lifenoodles, Horn of life, Vial of serum or Secret herb.
Poison is much less painful in Mother 3; it only causes damage equal to about 5% of your total health each turn. It can be cured by an Antidote. The attack message associated is usually "enemy bites with its venomous fangs!", although it is not 100% certain to cause poisoning.