1 Skin conditions and rashes. 2  Many skin conditions itch, including eczema (dermatitis), psoriasis, scabies, lice, chickenpox and hives. 3  The itching usually affects specific areas and is accompanied by other signs, such as red, irritated skin or bumps and blisters.4  Internal diseases. Drugs. 2  Reactions to drugs, such as antibiotics, antifungal drugs or narcotic pain medications, can cause widespread rashes and itching. 3  Pregnancy. 4  During pregnancy, some women experience itchy skin, especially on the abdomen, thighs, breasts and arms.