The rash is a red rash that usually appears as a consequence of certain infectious diseases (such as measles, scarlet fever, rubella, fifth disease, etc.), and are more common in childhood than at any other time life. They can be caused as a reaction to other causes: when they are caused by a virus known as viral rash; if accompanied by fever it is the so-called sudden rash that affects infants in their first year of life; sometimes they are the symptom of a disease of unknown origin, so the urgent attention of the child is required to assess and diagnose the severity, or if due to a drug reaction.