Chickenpox is considered as a disease of children because most people get infected when they are young. However, it can affect people of any age if they haven't had it before or vaccinated. It is caused by Varicella zoster virus which cause itchy rashes, fluid-filled everywhere on the body. Chickenpox is mild disease and will disappear by itself within one week without any specific treatment. Before rashes appear, there are nonspecific symptoms like: Feeling of weakness Lost of appetite Muscles pain Fever and Nausea Very small amount of people get complications from chickenpox such as: Secondary skin infection on the previous lesions Infection of the joint Lung tissue inflammation Brain inflammation You should go to hospital when you have anything like: The rash become redness and painful with swelling Severe joint pain with persistent fever Chest pain with difficulty in breathing Severe headache with vomiting