Threadworms

Threadworms are small worms that live in human bowels and are quite common in children. They lay minute eggs at night just outside the opening of the anus and the glue that stick these to the skin is itchy, so it is easy to scratch this area, even during sleep, and catch the eggs under the finger nails, which are then passed to whatever is touched where others can pick them up and transfer them to the lips directly or to something that is put into the mouth and spreads the infection. They can be treated by a combination of hygiene and medicines.