It's crazy how dismissive people are. My partner had a comprehensive allergy test done, the kind where they draw a grid on your back and apply different substances in each square.
You're supposed to leave and come back a few days later but my partner had a reaction in every square before she left the doctor. They asked if the interns could come take a look because they'd never seen such a complete reaction.
Not sure if it's what you meant, but I had a similar story where I reacted to everything, even the control. The allergist took that to mean "you're really allergic to everything," but I went looking for a second opinion who was able to get both the positive and negative controls to work. Turns out I'm not allergic to everything, the first allergist just didn't recognize benign dermatographia and was a bit too quick to ignore my positive reaction to the negative control. In all, it saved me a good chunk of change and sensitization risks that would have come from having unneeded components in my allergy shots.
I don't know the details of your case or if any of this applies, but if by chance you were in the same boat wrt the negative control it might be worth circling back for a confirmation test at some point.
I'm exaggerating a little, my partner has extensive allergies but not absolute. I jokingly say my partner is allergic to life but in reality it's just life on earth.
You're supposed to leave and come back a few days later but my partner had a reaction in every square before she left the doctor. They asked if the interns could come take a look because they'd never seen such a complete reaction.