The airline said the service from Heathrow to Philadelphia landed in the Irish capital because of an “odour”.
It added that “medical personnel met the aircraft” and two crew members and one passenger were taken to hospital “for evaluation”.
In air traffic control audio posted online, a pilot said two members of “cabin staff” had “lost consciousness”.
“I think they’re back to a state of consciousness now,” he added in a recording tweeted by Airport Webcams.
There were “general complaints about burning eyes and other problems with mucus in the nose and skin problems”, he said as he requested medics to “come on board the aeroplane”.
Passenger Katie Phillips tweeted that the jet was met by “firecrew, paramedics, police”.
The fluid was a “cleaning product used at London Heathrow”, the pilot added, which had been “left behind in one of the lavatories” and had seeped “into the carpeting”.
The label on the bottle, which was placed in a plastic bag, was “aircraft interior cleaner”, he said.
The airline said in a statement: “American Airlines flight 729 from London Heathrow to Philadelphia diverted to Dublin due to an odour caused by a spilled cleaning solution in the galley.
“The flight landed safely in Dublin at 1.15pm local time and taxied to the gate.
“Medical personnel have met the aircraft to evaluate any crew members or passengers who may need additional assistance.”