Luckily, there are a bunch of remedies for both ailments, and a lot of them cross over. Here are the best methods of healing Nausea and Cold:
Healing PSI (alpha for Cold and beta for Nausea) Cold Remedy (Cold) Cup of Lifenoodles (both) Horn of Life (both) Refreshing Herb & Secret Herb (both) Hospitals (all ailments) Saturn Valley & Tenda Village Hot Springs (all ailments)
Effects of Colds & Nausea
Both ailments will sap the afflicted character by a set amount of HP each turn. They will also suffer HP damage while walking on the overworld. If a character has a cold, they will sneeze each turn and lose 5 HP. Nausea is the more extreme version of a Cold, and afflicted characters lose 20 HP per turn.
What Causes Colds and Nausea?
In Earthbound, these ailments are inflicted by a handful of enemies. For instance, the boss Master Belch who is fought in Grapefruit Falls, has an attack called Nauseating Breath. Master Belch will later reappear in Deep Darkness, renamed as Master Barf, and retains this ability. A common enemy in Deep Darkness called Big Pile of Puke, will also use this attack. Enemies that cause the Cold status are a little more common. L’il UFO, found in Peaceful Rest Valley, will inflict the Cold status with its Night-time Stuffiness Beam attack. Also in Peaceful Rest Valley there’s an enemy called Spinning Robo, who also has this attack. During the initial events of Threed, you may encounter the Urban Zombie enemy. It can inflict the Cold status with its Breath attack.
Items To Buy for Curing Colds & Nausea
Luckily, status healing items are in abundance in Earthbound.
Cold Remedies cost just $22, and can be bought from Onett, Twoson, Threed, and Fourside. Refreshing Herbs cost $80 and they heal Colds, Nausea, and a host of other ailments. You can buy them from Threed, Saturn Valley, Dusty Dunes Desert, and Fourside. The Secret Herb ($380 each) has all of the above, plus a few other status effects, and can even revive unconscious characters. You can buy these in Saturn Valley, Toto, Scaraba, Dr. Andonut’s Lab, and Deep Darkness. And lastly, we have the yummy-sounding Cup of Lifenoodles item. This also has revival properties, as well as healing for Cold, Nausea, and a bunch of other illnesses.
Unfortunately, a Cup of Lifenoodles cannot be purchased anywhere. These are only found in gift boxes and chests. So the best items healing items & the most repeatable/practical ones to get would be Cold Remedies or Refreshing Herbs.
Other Methods of Curing These Ailments
If PSI abilities are more your thing, then ‘Healing α’ will just do fine for your Cold status. Or if you need to heal Nausea, then you will need the upgraded ‘Healing β’. But also, all major towns and cities in Earthbound will have a Hospital. You can visit any hospital and speak to the Doctor, who will be able to heal Colds and Nausea for a small fee. Or alternatively, you can visit the Hot Springs in Saturn Valley or Tenda Village. These heal all status effects, as well as providing a full HP heal for the party.
