What is this? My doctor told me yesterday that it was a viral rash like roseola. But it seems pretty scary to me! Should I go back and get it checked again?

You do not need to do anything if the child doesn't feel uncomfortable. But normally it will be quite itchy and you can apply calamine lotion to soothe it. If the rashes persist for more than 3 days, please visit PD. I hold the same opinion as Jorelle it doesn't look like roseola rashes. I suggest you to seek a 2nd opinion from another PD to confirm whether it is roseola or eczema.