Random rash on my daughters back

My youngest has some food allergies. Garlic being one of them and she gets hives often sometimes from just random things. All over her body.

This is on her back( red rash) and thigh (the small dots). This rash starts off like the small dots then overtime turns into what’s on her back and she’s so incredibly itchy (she has a drs appointment set up already) but we can’t figure out how to get her some relief/figure out what it is to help her. She is 2 and gets so upset with how itchy it is and she is starting to scratch herself raw.

Any ideas?