Police have appealed for any information and witnesses to come forward after the collision on the A49 in Upper Battlefield at about 3pm on Friday.
A silver Mini travelling south from Hadnall towards Shrewsbury collided with a black Nissan Qashqai driving north.
The drivers, both women, were taken to hospital by ambulance with one said to have been seriously hurt.
West Mercia Police said: "It is believed that the driver of the Mini suffered a medical episode at the wheel, crossed the carriageway and colliding head-on with the Nissan.
"The Nissan has then spun 180 degrees and come to a rest in the hedgerow. The Mini has then caught fire and members of the public helped the driver to safety."
Police are asking for anyone who witnessed the collision or have dash-cam footage that can help with our investigation, please contact us via our website quoting incident number 348i of 14 January 2022.
A spokesman from West Midlands Ambulance Service said on Friday that they were called at 3:06pm to reports of a two car RTC on the A49 in Upper Battlefield.
"We sent two ambulances, a paramedic officer and the Midlands Air Ambulance Critical Care Car with a trauma doctor and critical care paramedic onboard.
"We have treated a woman in a serious condition, she’s been conveyed to Royal Stoke University Hospital on blue lights and sirens for further treatment.
"A second woman has been treated for injuries not believed to be serious and has also been conveyed to hospital for further treatment.”
Shropshire Fire and Rescue Service scrambled two fire appliances from Shrewsbury with an operations officer.
Crews used breathing apparatus and a hose-reel jet to deal with the blaze where one vehicle was said to be 100 per cent involved in fire. Their incident stop message was sent at 3.40pm.