Can An Itchy Red Mark On Skin Be Due To Some Sort Of Skin Infection?

While in Mexico, my daughter developed a red mark on her arm that looks like she burned it on a curling iron. It was not itchy initially but now has become extremely itchy and is getting darker. The rash was a small area but got larger as the week went on. It does not appear to be spreading or getting larger anymore. My other daughter also has a small mark on her hand. I am worried about some sort of skin infection.