hives

I took my son to the pediatrician after notices Large welts all over his back, butt cheeks and stomach area. along with his arms. This has been going on for 5 days and one day his eyes began to swell.
After I bath him and give him claritin he seems to be fine. I have been also putting aveeno on him, but my pediatrian said it may be viral.
I know as a child and now an adult I have many allergies and am worried this may be the same with him.
There has been no changes in eating habits, laudry soap, animals nothing. We advised the pediatrian the only change was new soap we bathed our dog with.
Recently due to this I scrubbed my house in and out and he continues to get a onset of welts off and on. Should I be worried or wait like the pediatrian said and give it a month??