Girl red rash swelling tissue no fever After one full week hardly anything helps

Patient: 7 year old girl developed allergic like reaction during the night: eyes swollen, nearly closed, red blotches over whole body from head to soles of feet, itchy, painful, burning, no elevated temoerature. Was treated the next day with antihistamines…hardly helped, returned the second day to receive cortisone and more antihistamines. One week has passed and she has improved very little, and new blotches of this red colour (still appearing. She has not had any bites or eaten anything out of the ordinary. The he condition is ongoing after a full one week. Any suggestions please, she is very miserable Thank you in anticipation, Rita