Hello Welcome to healthcare magic forum. Thank you for your query I understand your concern regarding your skin problem. It look like you have allergic condition. But as it involve joint also we have to rule out rheumatic also. Vasculitis is another condition we have to think about. You need to consult doctor for proper treatment. If there is itching, you can take anti histaminic medicine. Stress, infection,heredity are common reasons for it. Avoid sun exposure and wear loose and cotton cloths. We should know about family history of the similar condition. I do not think it is viral infection. I hope I answered your question. Regards