The incident occurred at approximately 8pm on Friday night at a house on Connolly Road in the south Cork suburb of Ballyphehane.
A man forced his away into the house and attacked his victim with what has been reported as caustic soda, which is also known as sodium hydroxide. Caustic soda can cause serious burns and pain.
A 45-year-old man is being treated in hospital. His injuries are said to be serious but non-life threatening, and are to his head, face and upper body.
The man's two brothers were also splashed with the substance during the attack but their injuries are not believed to be serious.
Cork City Fire Service and the National Ambulance Service treated all three men at the scene using a decontamination unit, before transferring them to hospital.
Shortly after midnight a man was arrested. He is currently being detained at the Bridewell Garda Station in Cork city under Section 4 of the Criminal Justice Act 1984.
Gardaí have issued an appeal for anyone who was in the vicinity of Connolly Road between 7pm and 9pm to contact them if they witnessed anything suspicious.
Gardaí can be contacted at Togher Garda station on 021 4947120.
