Rash or dry skin on cleavage during pregnancy

I had something similar during my second trimester, the heat and sweat just trapped under the chest area made my skin so irritated and raw. What helped me was keeping a small towel or cotton cloth tucked there to absorb the moisture, and switching to loose breathable cotton tops. That said, since the skin is peeling and itching, it might be good to bring it up with your PD or gynae at your next visit, just to rule out anything like a fungal rash that needs a specific cream.