Thames Valley Police is appealing for witnesses following an assault which occurred in Milton Keynes on Friday evening.
At about 6.35pm in Wimblingdon Drive, Redmoor, a 24-year-old man was approached by two men who asked him for a cigarette.
When he reached to get one, an unknown chemical substance was sprayed in his face.
The victim did not sustain serious injuries but was taken to hospital for treatment.
The first suspect is a white man in his late 20s or early 30s. He is about 5ft 11ins tall with a slim build and was wearing a black or grey hooded jumper.
The second suspect is a white man, again in his late 20s or early 30s. He is about 5ft 11ins tall with a medium build and was wearing a white or grey jumper and dark jogging trousers.
Investigating officer sergeant James Sims said: “This assault could have resulted in a serious injury, and an investigation is underway.
“Members of the public can expect to see extra police patrols in the Redmoor area while our investigation takes place.”
“Anyone with information about the offence is asked to call the Thames Valley Police non-emergency number on 101.