The victim was outside the Today's Local convenience store at the junction of Harehills Lane and Coldcotes Avenue when a motorbike riding past sprayed the substance in his face.
Police say the pillion passenger on the motorbike sprayed the substance, which has been confirmed not to be acid, but more similar to bleach.
The attack occurred shortly after 2pm and the 55-year-old victim ran inside a nearby Asda for help, where he was given first aid and an ambulance was called.
The man is continuing to receive treatment for his facial injuries today, although they are not thought to be serious.
Police said on Wednesday that the suspects were riding a stolen silver Honda 125cc scooter and had their faces covered at the time of the attack.
They are appealing for any witnesses to come forward, and have given the motorbike's registration as BJ56 HTD. The bike was reported stolen on October 1 in Wakefield.
“While we have been able to confirm that the substance used was not acid, the nature of the attack is still a clear cause for concern and we are treating it very seriously.
“There is no obvious motive at this stage as to why the victim was targeted and we are treating this as an isolated incident.
“We are still keen to hear from anyone who witnessed the attack or who has any information that could assist in identifying the suspects.
“The silver Honda scooter the suspects used was stolen in Wakefield on October 1 and we would like to hear from anyone that has seen it either in the Harehills area yesterday or at any point since it was stolen.”
Anyone with information is asked to contact Leeds District CID via 101 quoting crime reference 13190516827 or call the independent charity Crimestoppers anonymously on 0800 555 111.