Hi My Husband Myself And My 7 Month Baby Are

hi my husband myself and my 7 month baby are covered in itchy rash like spots that boil up. we all have been scratching like crazy so originally I thought it was dry skin. I don't think its poison ivy because its winter in NH. My brother before going back to college from my moms house had the same symptoms and has been told its a rare form of eczema. but my mothers boyfriend has also had it for a while. my husband, child, and I all just moved into my mothers apartment. which is also really old. I don't know what to do. I am covered head to toe and itch like crazy so does my husband and recently I have caught my little baby scratching like crazy. Please can you give me some insight.