Nausea is a status condition that appears in both EarthBound and Mother 3. In EarthBound, it is simply a more extreme version of catching a cold, making the afflicted character feel sick in EarthBound or vomit at the start of every turn in Mother 3 and lose 20 HP. Like colds and poisoning, nausea lingers around on the overworld, and the nauseous character will lose 20 HP repeatedly as they walk.
In Mother 3, It still lingers around on the overworld, but loses its damaging properties in exchange for preventing the afflicted character from
Lucas and Party with Nausea
consuming food. It is usually cured by Healing or using a Fresh Mint.
Nausea is usually inflicted by Nauseous Monsters. And it can be afflicted by one of the attacks of the unused "Rope Snake" boss in Mother 3.