Police are now searching for two men in connection with the attack, which took place on Wednesday at 10pm in the Ilford area.
In a statement, officers said they wanted to speak to William Deo, 20, and Gavin Okwu-Brewis, 29, and have warned members of the public not to approach the men.
The victim, aged in his 20s, was taken to an east London hospital, where he remains.
The substance used in the attack is believed to have been ammonia.
Anyone with information can call police and quote the reference 8771/13 June.
Crimestoppers can be contected anonymously on 0800 555 111.