Smiting Sickness
Smiting sickness is caused when angels release an immense force of power on Earth, causing fallout to poison the surrounding area for some miles. If a human ventures into an area that has fallout, they will become disoriented and begin vomiting the closer they get to ground zero. The symptoms are so severe that they cannot be healed by an angel, with the effects of the sickness becoming worse the closer a human gets, Lot's wife having turned to salt due to her proximity to a smiting event. This fallout does not affect angels.[1] Smiting of this magnitude rarely happens on Earth, with the destruction of Sodom and Gomorrah and the two attacks on Amara being the only known cases.
Episodes
11.10 The Devil in the Details
When driving towards the scene of the massive smiting inflicted upon Amara to find out whether she's alive or dead, Dean finds his vision becoming distorted when he's around a mile away from ground zero. Stopping the Impala, he stumbles out and vomits multiple times. Eventually, Castiel appears and checks him over before telling him he has smiting sickness. Dean is surprised that's an actual thing and asks if Castiel can heal him. Castiel tells him that he can't and that Dean needs to turn back.
11.23 Alpha and Omega
A similar smiting is launched against Amara in 11.22 We Happy Few. However, there is no sign of smiting sickness afterwards, with the Winchesters and Rowena MacLeod being able to stand in close proximity to ground zero without suffering any harm from it due to God protecting them.
