I am sorry to hear that your daughter has been treated for pinworm, and is still having problems with her bottom itching. Pinworm, or Enterobius vermicularis, is a small roundworm that can live in the intestine of humans. It it usually transmitted from one host to another through the fecal-oral route. Meaning that the eggs are transmitted in the feces (on in this case sometimes around the anus) and often poor handwashing technique or practices to another person. Then if they tough their mouth, or food that they put in their mouth, the eggs are passed to a new host and they will hatch in their intestines. Pinworms have an interesting life cycle however...the gravid female worms migrate from the colon to the anus (typically at night) and deposit their eggs externally around the anus. Some think that they need oxygen to become viable. The female worm then typically dies. They can deposit thousands of eggs however prior to dying. The combination of the dead female worms, and the newly deposited eggs cause an allergic type inflammatory reaction in the skin around the anus which is very itchy. These eggs can stay viable for up to 17 days in a moist environment. Despite being treated, this itchy reaction may be present for a few days. I would recommend cleansing the area with soapy water, and very good hand washing for the next couple weeks to prevent passing the infection on to anyone else in the household. If she continues to have problems after a few days having completed treatment, I would recommend making an appointment with the physician that treated her for the pinworm for a follow-up. I hope this helps.