I noticed my 4 year old son has small worms on his anus. He has numerous scratch marks on the anal skin and this is how I noticed the worms. How do I get rid of them?

The only way to get rid of these worms (pinworms) is take a medication known as mebendazole. This drug will kill both the mature worm and any newly hatched eggs. 

The treatment has to be repeated a week later to ensure no more worms are present. In the meantime, maintain excellent hygiene at home. Make sure everyone in the family washes the hands frequently. Bathe your son at least twice a day to get rids of the eggs near the anus.

These worms can easily be transmitted to other members of the family. Wash all linen separately and get the treatment as soon as possible. Pinworms by the way are not life threatening.