Scientists believe up to 25,000 creepy-crawlies are hiding behind the lights, baubles and tinsel of the average Christmas tree.
Experts say the act of bringing a festive fir into a warm house sparks life into thousands of sleeping bugs.
Bjarte Jordal, an associate professor at the University Museum of Bergen, Norway, said the most common creatures to be found among the needles are lice, mites, moths, springtails and spiders.
He said: “They hibernate for the winter and usually empty their bodies and fluids, produce a chilled liquid and become completely inactive.
“But they reawaken when the tree is brought into the heat of the living room.
“If you pound the tree on a white cloth before you throw it out, you discover quite a number of small bugs.”
Prof Jordal also warned that severe allergy sufferers can react badly to a large number of tiny insects in a tree.
But he added: “The bugs mostly live inside the tree and, with no food on offer, quickly dry out and die.”