My 6 month old puppy has a rash

I adopted a yellow lab mix from the animal shelter yesterday and thus haven't gotten to get her into a vet yet, but she has a very big rash on her belly. Maybe she's allergic to something? And a spot on her face, by her mouth. It doesn't seem to bother her, but the one on her mouth started bleeding a little earlier. Any suggestions on what this could be?

Has she been kennelled in the shelter for any length of time?

The one on her belly could be from laying on damp concrete perhaps the one on her face too if that area has been in contact. It does look like an allergy rash, but it's always important to have a vet check these things out to make sure that she gets both the correct diagnosis and, of course, treatment