my son had a a lowgrade fever for 3 days, about 38 to 38.4C accompanied with stuffy and running nose. Fever subsides on the 4th day and he was as active as ever and never felt like sick. just this afternoon, rashes came all over his face and neck. and it felt like its itchy because he keeps on scratching. I noticed too, that behind his ears is kind of swollen or has bump..i cant figure it out if its measles, rubella, or dengue fever..what should i do?