American Airlines flight AA729 from Heathrow to Philadelphia was rerouted to Dublin airport at around 1pm this afternoon (UK time).
It is understood a bleach-like cleaning product was left in the plane’s toilets at Heathrow and spilled out of its container and into the floor.
After the flight took off, the smell of the liquid left passengers and crew suffering ill effects.
The captain radioed air traffic control to request a reroute after number of passengers suffered burning eyes and itchy skin.
A passenger told MailOnline: ‘A cleaning product apparently leaked and some people felt ill. We were informed of this prior to take off and thus delayed an hour.
‘The plane still took off and then an announcement later told us, about one hour into flying time, that some crew members are feeling ill along with a few passengers and we have to make an emergency landing in Dublin.
‘Paramedics and the fire brigade came on board and investigated and took care of the ill people.
‘We are now stranded in Dublin and American Airlines have put us up in a hotel nearby until further notice. We still don’t know if we’ll make it to the US tonight.’
Footage filmed on board after the flight landed shows paramedics helping people who are heard coughing or possibly vomiting.
The Airbus A330 had 287 passengers on board and 12 crew when the emergency landing was called.
A spokesman for the airline said: ‘American Airlines flight 729 from London Heathrow to Philadelphia diverted to Dublin due to an odor caused by a spilled cleaning solution in the galley.
‘The flight landed safely in Dublin at 1:15 p.m. 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.’