Thanks for writing in.
lesions are usually in web spaces of hands and feet as well as body folds. Itching will be worst at night.
I would like to know age of your sister. There is one condition called impetigo contagiosa
seen in kids which is usually bacterial infection.
In elderly or middle age, other condition presenting with same appearance is molluscum contagiosum
Clinical examination plays an important part to diagnose condition. So I would recommend you to consult dermatologist
before lesion leave scar marks.
I hope I have answered your query. Revert back in case of any doubt.