A 41-year-old man was taken to hospital after being "pepper sprayed" during an alarming attack in Bathgate town centre.
Police were called to George Street at around 11.25am on Friday, when the area would have been busy with shoppers, after receiving reports of the incident.
Officers say the victim was sprayed in the face with a "noxious substance" following an altercation with another man.
The suspect then walked off, and police are currently trying to trace him. He is described as being white, in his mid-30s and he was wearing dark clothing. He was also carrying a walking stick.
Police want anyone who has information about the incident, or knows the identity of the attacker, to come forward.
Detective Constable Sam Plastow, of Livingston CID, said: “The man who was assaulted was taken to hospital and returned home after treatment. Fortunately he has not suffered any long term effects as a result of being exposed to a noxious substance.
“It was the middle of the morning and the street would have been very busy at this time with people shopping and going about their day-to-day business and we would like to speak to anyone who saw what happened.
“If you have any information please call Police Scotland on 101, quoting incident 1209 of Friday, 7 February, or contact the charity Crimestoppers anonymously on 0800 555 111.”
