1/2 inch is fairly sizeable. I would want the vet to take a look. When did your pup have the vaccination? It could be the injection site.
Teddy had sizeable lump once that our vet and I believe was a spider bite, or it could have been a bee sting. It was flesh colored, between his shoulder blades.
Cost of our vet visit was a routine exam and we received meds, a topical and oral.
__________________ Kristin, Max and Teddy |