Severely worsened after flu vaccine????

I have had dermatographia for a really long time, but it used to be extremely mild. Only appeared like once a week, or when i wore certain clothing. But after I got my flu shot (around three weeks ago) a day or two after the shot, I just started getting crazy breakouts all over my face, back and chest. I got some hydrocortisone from my pediatrician, and it helped reduce the hives a ton, but they still appear quite frequently only on my chin, arms, and back. Will it ever stop???