BoboB
Don't worry! I have such experience. My daughter, Cheuk Yiu, has fever on 27 Jan night. It's around 39C, I, therefore take her to the hospital's emergency immediately in order to reduce temperate. I took her to see private doctor the next day because of 全身出哂紅點. The doctor said it's 玫瑰疹, it's normal that he didn't gave any medicine except the 退燒 medicine. He said no medicine can help at all. But, beware that not to let the baby get cold.
Cheuk Yiu was then ok the next two days, and the 紅點 disappear accordingly.
To play safe, take him to see doctor tomorrow la!
Get well soon!
Selina