The first thing to do when your child develops a rash is to reach for a tumbler. Run the glass over the rash to see whether it disappears under this mild pressure. If it doesn't, it's a known as a non-blanching rash and can be a sign of serious infection.
This is a companion discussion topic for the original article at https://patient.info/news-and-features/rashes-every-parent-should-be-aware-of