I think my dog has trauma? (srs)

im gonna go into this with some background info: ive had my dog for three years, hes an american pocket bully. Hes an absolute sweetheart too. His name is phantom, here is a picture of him.

Onto the story, 

A couple days ago my mom had dmed me on instagram saying that Phantom was breaking out in welts and he couldnt stop itching. I had told her to take him to the emergency vet closest by, she did, and she had informed me that the welts had kept multiplying and spreading even farther on his body. Now my dog has pretty bad allergies so he cant eat a lot of food, but we have NEVER seen a reaction this bad before. 

The vet had said that he had a severe allergic reaction to something and that he was bitten by something venomous ON THE BALLS. like DUDE imagine getting bitten by a spider in the nuts. So now my mom had to rub cream on his balls twice a day and give him medication. 

Ever since this happened (its only been two days), he has been shaking and peeing around the house. i think he has trauma from this situation because he has never acted this way before.