[little coco]

Hi everyone, I hope someone can help me out? My Yorkie, Knuckles, has some red raised bumps, almost looks like pimples on his tummy and then a few on the back of his neck, and then one by his eye.
Is it possible for dogs to get poison oak, or ivy? He was running around the woods yesterday, and these bumps just showed up overnight.
I gave him a bath tonight,maybe that will help. He doesn't itch them or anything, thus far. He has a vet appointment this coming Mon. but if his condition doesn't improve tomorrow, then I'll take him sooner.
If anyone knows what this might be, I'd appreciate the info.
Worried mom.