What could this be. Ps. It’s not bed bugs.

One of my twins has had these hives for a month now and she is on daily antihistamines. If she doesn’t take it this is how bad it can get. And she itches. At first the gp thought it could be bed bugs but we inspected house plus she sleeps with her twin and myself and neither of us have anything at all. I even moved her to her sisters cot and she still gets them. I can’t figure out what she can be allergic to. I’ve requested for blood work today but they said the soonest appointment will be 28th May. I was just wondering if anyone has any insight.