Hello, I understand your concern. Scabies is a very tedious infection which spreads very easily by human contact. There are more than one reason why treatment has failed. First of all, in order for the scabies to be eradicated it is of utmost importance that all family members be treated at the same time. The treatment consists of applying anti scabies lotion twice, one week apart. Second, there is a possibility that medication was not applied properly. If using a lotion in children, it is very likely that it can wash off in certain areas especially the hands. Let me remind you that anti scabies lotion is applied on the entire body, especially in body creases and between finger webs, except head and neck. A third reason for treatment failure could be resistance to medication. It is possible and well documented with Lindane, Crotamiton and Benzyl Benzoate. Only a few cases of resistance to Permethrin are known. Besides lotions, there is also an oral anti-scabies drug, Ivermectin, which is just as effective as Permethrin and no cases of resistance to it are known. It is also worth mentioning that itching can persist up to six weeks after the treatment. I hope this helps. Wishing you and your grandkids good health.