Smith was on 80 not out on the fourth afternoon, his latest epic knock of the series, when he was struck in the neck by a steepling delivery from the debutant.
Smith, who had already received treatment for a nasty blow on the left forearm and fended off a lightning fast 96.1mph ball aimed at his ribs, hit the deck immediately and remained on the floor for an extended period before stumbling to his feet.
Members of both teams' medical staff attended to him and the 30-year-old was eventually persuaded to leave the pitch, despite being seemingly reluctant to do so.
Smith was applauded from the field, with his side 55 behind on 203 for six before he returned, following extensive checks, to resume his innings.
A Cricket Australia statement read: "Steve was hit on the neck below the left ear. He was assessed lying on the pitch at the instructions of team doctor Richard Saw.
"Dr Saw made the precautionary decision to remove Steve from the field of play to have him further assessed under Cricket Australia’s head impact protocol.
"Steve then passed his assessments and will now be monitored on an ongoing basis, as is routine."
Smith's innings finally ended when Chris Woakes trapped him lbw for 92, the first time in this Ashes series England have done so for less than three figures.