From your history it looks like your daughter is having either exanthematous rash
or acute urticaria
. The cause for both can be the Gastrointestinal infection
Acute urticaria will have well defined raised wheals in various shapes and they are transient. They are usually very itchy.
Exanthematous rash is diffuse, blanches on pressing with your finger, usually non itchy, if itching is there it is usually mild. It usually starts over the face and progresses downwards. It subsides by itself. Application of calamine
lotion frequently will soothe the skin and decrease itching.
Hope this helped.