What are common causes and treatments for my itchy rash?

Depends: Allergies. Chemical contact. Dry skin. Sensitive skin. Dry air. Allergy to a medication. Allergy to makeup. All possible causes. Treatment would depend on the cause.

Depends on the cause: There are many things that could cause the skin to itch. Several types of inflammatory conditions of the skin, allergic reactions, and sometimes bacterial, viral or fungal infections can cause rashes on the skin. Insect bites can also be the cause of a rash on the skin. Have it evaluated by a professional and get the appropriate treatment.