Two masked attackers grabbed his watch and rucksack as the 29-year-old clasped his hands to his face in Epping, Essex.
The attackers had pulled up in a black car as Giovanni was about to get into an Uber, and sped off afterwards.
Giovanni — who returns to TV tonight in the pre-recorded launch show forBBC1’s new Strictly series — was treated at the scene by paramedics.
He was understood to have avoided any long-term physical damage from the attack — and has told friends he now believes the noxious substance was
Last night a source close to him told The Sun: “His first thought was that it was an acid attack — because of the burning in his eyes.”
“He has been left absolutely terrified by the attack. It has hugely knocked his confidence.
The source added: “As a person in the public eye, Ashley is just as concerned that this kind of thing could happen to her too.”
Police are investigating the crime, which took place at 8.30pm one day last month.
Giovanni is the fourth Strictly pro to be attacked.
Pasha Kovalev, 39, was robbed of his mobile phone by moped muggers in London in June.