A pregnant woman is one of three people to have been hit by bleach thrown by someone in a passing car.
The woman was walking with a man in Manchester when the bleach was thrown at them by someone at about 8.10pm on Friday.
Both victims were hit in the eyes and suffered "severe discomfort" but no lasting damage, police said.
Around 20 minutes later, a third person was hit with bleach thrown from a passing silver Ford Fiesta on the same road - Ashton Old Road in the suburb of Openshaw in the east of the city.
The man was not hurt but the bleach hit his back and stained his clothes.
It is not known whether the first two victims knew the third.
Inspector Cherie Dunn, from Greater Manchester Police, said: "I am so thankful that none of the victims of these senseless attacks have been seriously injured.
"We could easily have been dealing with life-changing injuries.
"Not only that, the woman is pregnant - the worst case scenario does not bear thinking about.
"Bleach attacks could have had catastrophic consequences."
The attacks come after a 22-year-old woman and a 24-year-old man were both blinded in one eye after a noxious substance was allegedly sprayed in a nightclub in east London.
Some 20 people suffered burn injuries, with 12 people attending hospital.
Figures from police forces across the UK suggest that the number of assaults involving corrosive substances has risen by 30% in two years, BBC Radio 4's Today Programme reported.
The number of attacks in London increased from 261 in 2015 to 454 last year.