This is because the worms are most active at night. This may lead to disturbed sleep or infection where the person has been scratching. Sometimes a child might wake in the night with severe pain around the anus, which can be relieved by placing the child in a bath. An infected person may have no symptoms but sometimes worms can be seen in the stool or on the toilet paper. They can often be passed around within families.
Threadworms leave the bowel at night and lay eggs on the skin around the back passage.
The eggs frequently cause itchiness. Eggs may get onto the hands or under the fingernails of the person infected through scratching of the itchy area and because of inadequate hand-washing after using the toilet. That person then may pass on to an uninfected person, for example through food handling. Eggs can also get onto carpets, bed linen, towels, facecloths and into household dust and be passed to other people in this way. It may be between 2 and 6 weeks after contact with a source of infection before the life cycle is completed and eggs are laid in the newly infected person.