Eight fire engines and around 60 firefighters were called to a fire at a shop with flats above on Winchester Road in Highams Park.
The first floor, roof and rear extension were destroyed by the fire. One woman and one man left the building before the Brigade arrived. They were treated at the scene for smoke inhalation and taken to hospital by London Ambulance Service crews.
The Brigade was called at 1238 and the fire was under control by 1500. Fire crews from Chingford, Walthamstow, Leyton, Leytonstone and surrounding fire stations were at the scene.
The cause of the fire is under investigation.