Itching is a common symptom of lupus which is a part of MCTD. The inflammation increase during a flare can release histamine like in allergic reactions. Antihistamines can help as well as antiinflammatory meds. I would try generic Allegra, (fexofenadine) and if insufficient try an H2 blocker like Famotidine ( generic Pepcid) along with the H1 blocker. They seem to act synergistically.