Not sure what you mean by "mites". What you describe and the treatment you were eventually given, seem to indicate that what you had was "scabies". Yes, these are tiny mites that burrow under the skin and lay eggs. It's the eggs hatching and the larvae burrowing out that causes the dreadful itching.  My mother-in-law (now 85) had it two years ago and suffered for months, having been given all sorts of useless emollient creams and told she was exaggerating the symptoms, before it was finally properly diagnosed by a dermatologist.  But since the sufferer here has been to dermatologist, I hope that they would have checked for scabies and ruled it out.  Worth asking, perhaps?  And if so, it will take more than just one application of the special lotion, at least two, at a specified interval to make sure that the hatchlings are killed as well. Even so, it takes time for the itching to disappear completely, months more than weeks, in my mother-in-law's case.

Hope she finds the cause and gets some relief from the itching soon.