My son is 10 years old is facing Itching in few body area due to which his nail or scratches the area due to itching and few time little blood. White colour spot is seen over the skin when it get dry. We already examined the problem with few dermatologist but after few month treatment of applying cream and usage of soap zyndet it gets cures. But later same is back again once course is completed..... It is the problem from last 3-4 years. Now what can be done to solve the same permanently??