Why does my dog have a red spot right under her chin?

It's pretty small in size. And directly under her mouth almost like its on her lip It's red and looks pretty nasty. I've looked up "canine acne" and It doesn't look like the pictures. The "red spot" has no hair and almost looks as if she's scrapped her chin really bad. I can see her hair follicles but there's no hair on this nasty looking spot. She's a mix and about five years old.

Not sure what it is, but there are a couple of possibilities.It could be a food allergy and spots can occur on his face and/or body, and appear as hives or would be red and very itchy.Other possibilities would be canine acne, caused from Staph bacteria, or some other contact irritation.Feeding him from a stainless steel bowl, or ceramic would be the healthiest. And also a non-plastic water bowl would be best. If in doubt take him to the vet to have it checked out.