Yeast infection???

I am beside myself with my b-inlaw... his dog Sadie who is about 3 years old has had this rash on her tummy around her nipples and belly area for over 2-3 weeks now, I kept telling him to take her into the vet and he kept saying that it was what she always gets and it is due to her immune system and that he had the medicated shampoo and had been giving her baths etc.... well we went away on vacation for a week and then came home and we were watching her for a week for him while he was out of town, well the night we got home and started watching her I felt terrible! Her poor belly and nipples were so red and swollen and it stunk, my first thought was a yeast infection. I have smelt it in dogs ears before but not from a belly. I freaked out I called him and said gee thanks for leaving her in this condition under my care, and asked what he was giving her for it, his response was nothing... Well I was pissed, I had about 4 clavomax left over from my dog Zeke and I gave her one a day for the 4 days that I had on hand, well wouldn't you know the rash and swelling went down in 24 hours, and just turned into pinker looking skin and not red and swollen, so I called him and told him what I did and said as soon as you get home YOU Will take her to a vet and I told him that it was cruel of him just to think it was the same old stuff!!!!

My question to you is, can food allergies cause a yeast infection on the stomach of a dog, cause it never really ever seemed to make her itch but it did go from small pink rash to full blown red and swollen in a weeks time. She had mange when she was a pup and was given the diagnosis of immune deficient just cause she had mange when she was a few months old, I think alot of that came from where he got her too tho (BYB)....It does not seem to be seasonal with her cause she gets it on and off all year long... the reason I am asking if it is from food is cause he gives her all sorts of people food and I am always yelling at him not to do that because it is not good for her. Her regular dog food is Canidae and that has only been in the past year cause she was having these flair ups constantly on her other dog food (Purina) and suggested that he change her food and it helped for a while and kept the occourances to a minimum, but do you think people food can trigger these reactions??

I have tried to suggest things to him but he is one of those know it alls and this is the first dog he has ever owned and is not very experienced in that aspect, but he will tell you differently if you ask him, then again I think he, thinks he knows everything even if he has never done it....LOL!!!

Oh by the way he did finally take her to the vet yesterday after me harping on him about it, he thought he could just call up the vet and say perscribe me something for her rash with out taking her in, I said yeah right there is no Dr that will do that!!!! any way I won that battle... She has a yeast infection on her stomach, her left ear and between her toes on all of her paws and from the looks of it probably on her private area. The vet loaded him down with 3 different meds for this poor pup to take on a daily basis till it goes away.....

Sorry for rambling but I have been frustrated for a few weeks over this!!!