Whole family suffering body itchings.

I am 36 years old and having two children. daughter 7 yrs & son 4 yrs. We are living in a house of two rooms and one hall. We are living in one room and one more family living in other room in the same house. We all share the bathroom and hall.  From last 10 days my family of four are suffering body itchings. But not the other family. I thought  it may be due to water or clothes. So we all started to take hot water bath  and changes clothes on bed and wear the good clothes at all time. I changed my bed matress and bed sheets. Went to doctor and he gave memotosone.There was no use at all with that. Still we all four are scratching our full bodies at whole day. Unfortunately having the itchings at our private parts also. We really getting panic and not understand what is the issue with us, while the other family in the same house is not having these.. I really don't understand why it is, inspite of good hygiene. we URGENTLY need a cream or medicine to stop itchings immediately. Please..