Dog Red Bump That Looks Like A Blister. It could be an infection, cyst, allergic reaction, or mass. My dog has a red looking wart on the inside of leg, doesn't to bother her, almost looks like a blood filled skin tag.
It initially looked more red, like it was a blood blister, but the color has faded somewhat. The bump will probably appear pink or red, and it may even look like a big pimple. I'll do all i can to help.