Four fire engines and around 25 firefighters were called to a fire at a flat in Lowe Close, Chigwell.
Most of a ground floor flat was damaged by fire. One woman left the flat before the arrival of the Brigade and she was treated at the scene for smoke inhalation before being taken to hospital by London Ambulance Service crews.
The Brigade was called at 2125 and the fire was under control at 2219. Fire crews from Romford, Woodford, Ilford and Dagenham fire stations attended the scene.
The cause of the fire is under investigation.