If your child develops a rash after having a fever, you might be concerned. Here’s a look at common rashes in toddlers like roseola, and treatment options. Fevers are an indication that your body is trying to fight an infection. If your child’s fever is higher than normal, it’s best to seek medical attention. fever and rash in adult. MarieElizabeth I had a fever lasting 4 days: no diarrhea, but I dad have some strange aches in my stomach area. In adults, several types of skin inflammation, various allergic reactions (contact dermatitis), and sometimes infection with a mite or virus can be the cause of a new rash on the skin. Determining that the skin change is recent (generally happening for the first time and lasting less than weeks) helps to narrow the possible causes for the rash.