A woman has allegedly thrown acid on a man in Bhawani Ganj under Maurawan Police Station area here.
The incident took place in the intervening night of Monday and Tuesday.
The man and the woman, both in their 20s, were neighbours.
Vinod Kumar Pandey, Assistant Superintendent of Police (ASP) Unnao said, "We have come to know that they are neighbours and had been in contact with each other for several months. The man has been sent to a hospital while the woman is being questioned."
Investigation in the case is underway, Pandey said.