Witnesses are needed after a woman in her early 30s had a suspected noxious substance thrown at her in the middle of a Brentford street on Friday evening (June 9).
The injuries she sustained in the suspected acid attack were not life-threatening and she did not need hospital treatment.
A Metropolitan Police spokesman said: "Police were called at approximately 7.10pm on Friday to reports of a suspected noxious substance attack on Brentford High Street.
"Officers attended along with the London Ambulance Service.
"A woman, aged in her early 30s, was treated at the scene by paramedics for injuries that are not life-threatening or life-changing. She did not require hospital treatment."
Officers are appealing for witnesses to the suspected attack and urge anyone who may have seen what happened to contact them.
A 20-year-old man was arrested at the scene of the incident on Friday on suspicion of causing grievous bodily harm.
He was taken to a west London police station and has been bailed to a date in early July.
Enquiries into the incident continue.
Anyone who witnessed the incident is asked to contact police on 020 8247 6222 or via 101 quoting 6934/8June or call Crimestoppers on 0800 555 111.