Allergy, Ringworm or something else.
My dog Buddy, is a 7 year old Boston Terrier. He is 25lbs and is in good health. The past month he has had a red blotchy rash in between his thighs. I have changed his food in the past couple months. He does not itch it and he doesn't care when I touch it. I give him a Benadryl but it does not seem to change the redness of the rash. I will be changing him over to sensitive skin and stomach dog food and non scented laundry detergent tonight. I just want people's opinions on wether I am going in the right direction or not.
This sure sounds like one of those mystery cases! I would exclude ringworm since it's appearance for the most part is roundish patches with no hair. Allergies, could be, but he's not itching or scratching and the Benadryl should have helped, at least a bit. So I voted something else. Your best bet? Have your vet see it and possibly do a skin culture to rule out bacteria, fungi and yeast.
Because of the location, I am aiming towards some form of contact dermatitis. So I would look where is laying on. Blankets, grass, floor, could be culprits. You are doing good to change laundry detergent and perhaps even what you clean your floors and carpet with. With food allergies, it's more likely to see a generalized rash and itch on the whole body, since this is localized, I think of some form of contact issue.
I voted allergies because I have seen some allergies develop with a rash on the abdomen and thighs. However, it could also likely be so many other things. I second getting a skin scrape done to exclude bacterial infection, fungal and yeast infections or some parasite. Could likely be a contact dermatitis, but I see some redness as well on the abdomen.
Also, good idea to ask about thyroid testing as low thyroid levels at times can causes skin irritations.