Funny Rash

Question
My English Bulldog is 6 and a half years of age and we absolutley love him. Recently he developed a dark, blackish-colored rash on his inner left thigh. It seems to itch him and has appeared to have gotten bigger..any idea what this might be? Should we take him to the vet? Any advice would be great..thanks.  

Answer
This sounds like a contact dermatitis, perhaps from laying in the wet grass or perhaps a new carpet cleaner? It will take some detective work to figure out what's causing it but give him a Benadryl and see if that helps. If it does, you know it's an allergy to something. If it doesn't, he needs to see the vet.  If it does help, you can give it to him safely a couple of times a day.  This has been an exceptionally hot summer.  That could be the culprit.