I would recommend treating a child the same way you would treat an adult, except in lesser amounts based on the child's weight. Our bodies function the same way. We need cleansing and rebuilding.
I've added some info. for a natural Morgellons and parasite treatment to my site. Have a look there to get more info. If you have questions, there is a form on the page.
Whether your child has Morgellons or some other parasitic infection or digestive problems, the basic principles are the same. You want to give their body the nutrition (in the form of herbs and whole food supplements) it needs to rid the body of parasites and build up and strengthen the immune system.
I hope your child is well again soon. It's hard on them, but I'm sure it's hard on YOU to see them suffer.