Itching at legs. Test for the baby?

My baby is 19 months old and having itching problem at legs from the age of 6 months. We showed to few dermatologists and they suggested few lotions like dermadew and soap. We used it, but no improvement. Doctor also suggested to use Hydroxyzine syrup atarax for two weeks. During this syrup medication the itching got relieved, but it started happening again after few days. This is the case from one year. When on medication, the itching stopped and started again after few days. My wife also having itching problem from 8 months and the baby still having mother's milk. What we have to do, because mother is having itching problem and so the baby still having mother's milk and because of this itching will occur to baby also? Do we need to do any of the blood test for the baby? If yes, what is the test name.