Pinworms (Enterobius vermicularis) are small worms that live inside the large intestine. They cause intense anal itching, especially at night when the female comes to lay her eggs in the anal region. Pinworms are the most common parasite, and about one third of Canadian children will have pinworms at some point in their life. Pinworm testing consists of collecting eggs around the anal area using the Scotch tape test. The tape is then examined under a microscope. The test is often repeated several times to increase the chances of detection. Results are reported as either negative or positive.
A positive result confirms the presence of pinworms in the intestine. Repeated negative results indicate that pinworms are probably not responsible for the reported anal itching.