There are actually many rashes that do not hurt or itch. Usually, the most common type of rash that does not hurt or itch is purpura. There are allergic purpura and stress purpura and also abnormal platelet purpura, including thrombocytopenic purpura or thrombocythemic purpura. There are viral rashes that are also painless, such as measles or rubella, etc. There is also pityriasis rosea, which is also painless in some or most people. There are also specific urticaria that are also painless, such as giant urticaria, also called angioneurotic edema, which is also painless.