Roseola (roseola infantum) is a mild and harmless illness most common in children 6 months to 2 years of age. It is caused by two common viruses which belong to the herpes family but which do not cause cold sores or genital sores. The viruses are spread through droplets from coughing and sneezing. The main symptom of roseola is a sudden, high fever -- 103F-105F - that can last for up to 8 days and then quickly subsides, leaving a pink rash on the trunk , neck, and arms that may last up to 2 days. Diagnosis is made by the distinct rosy-hued rash left in a fever's wake. Treatment includes fever reducers and sponge baths. Roseola can cause fever seizures because of the rapid increase in temperature. Follow the links below to find WebMD's comprehensive coverage about roseola, what it looks like, its symptoms, treatment, and much more.