My daughter developed a rash on legs, may have been bug bites?

My daughter (24yo caucasian) recently had an overnight layover in Xianmen China and noticed the next day what looked like bug bites over much of her body. The bites are not itchy, but there is a growing irregular shaped dark red rash around most of them. The attached photo shows the progression from mild redness on day 2 to dark red irregular rash on day 4. She doesn’t think she has a fever, but has felt some perhaps unrelated instances of nausea and headache. She’s currently in Japan for an extended stay.