The 28 year-old suffered severe burns after attacking the arachnid with an aerosol can at his home in Clacton in Essex.
The man was summoned by his wife to deal with a spider she had seen scuttling behind the lavatory on Bank Holiday Monday. Not being able to reach it, the man decided to kill it by spraying it with the can.
However he was unable to see whether it was dead because the bulb in the bathroom light had blown. At this point he turned to a cigarette lighter to illuminate the room, but in the process ignited the gas fumes and caused an explosion.
The blast was so strong it blew the man off his feet and lifted the loft door off its hinges.
He suffered flash burns to his head, legs and torso and was rushed by ambulance to hospital after dousing himself in cold water.
A spokesman for Essex Fire Service said: “It appears the wife had spotted the creepy crawly in the bathroom and asked her husband to capture it.
“He sprayed it first with an aerosol where it was lurking behind the toilet bowl and when that didn’t appear to work, he lit up his lighter to spread some light on the situation as the bathroom bulb had blown.
“There was an almighty explosion which blew the man back into his hallway and lifted the hatch on the loft.
“He did exactly the right thing by jumping into the shower and cooling his burns with cold water while his wife raised the alarm.”
Firefighters administered emergency first aid at the scene while waiting for ambulance teams to arrive.
A spokesman added: “We’re not entirely sure whether the spider got away or not but there was no sign of it at the scene.”
Ambulance crews treated the man for burns to his arms, legs and face and breathing difficulties and he was taken to the Colchester General Hospital, in Essex, where he was given pain relief and discharged in the early hours of Tuesday morning.
In June last year Simon Elsey, 40, from Rotherham, suffered severe burns after a can of hairspray exploded at his home. The canister had been left on top of a children’s fireguard in front of a lit fire in the sitting room. The blast was so powerful it blew out two window panes and the can was found embedded in the ceiling. Mr Elsey had been asleep in the sitting room at the time and firefighters said he was lucky not to be engulfed in flames.