Natasha Timarovic, 27, was cleaning her teeth at in her home in the Croatian city of Zadar when lightning struck the building.
She said: "I had just put my mouth under the tap to rinse away the toothpaste when the lightning must have struck the building.
"I don't remember much after that, but I was later told that the lightning had travelled down the water pipe and struck me on the mouth, passing through my body.
"It was incredibly painful, I felt it pass through my torso and then I don't remember much at all." Doctors at the city hospital where she was treated for burns to the mouth and rear said: "The accident is bizarre but not impossible."
She was wearing rubber bathroom shoes at the time and so instead of earthing through her feet it appears the electricity shot out of her backside," a medic told local newspaper, 24 Sata.
"It appears to have earthed through the damp shower curtain that she was touching as she bent over to put her mouth under the tap. If she had not been wearing the shoes she would probably have been killed by the blast."
24 Sata said the young woman had been released from hospital after being kept in overnight and was expected to make a full recovery.
