The Metropolitan Police attended the University of Greenwich after a man was “attacked” shortly after midnight on Tuesday.
The man was treated for head injuries by the London Ambulance Service before being rushed to hospital.
The suspected attacker remains at large.
A Met Police spokesperson said: “On Tuesday, 10 December police were called to Avery Hill Road, SE9 at 00:13hrs following reports that a man had been attacked and sprayed with an unknown substance.