My pit ‘Spike” developed a spot on his neck that was an open sore. The vet said the cloth collar was holding the infection that was caused by-red dye in his food. I then checked and found it in most (dry) dog food. The dog’s “siblings” also had issues with it with ear infections. Once taken off it took like a few weeks and it cleared right up. He asked me to notify the maker- (Purina) that I did and for what? They continue to sell it and now real nasty food killing dogs.(Beniful)
I have never heard of red dye in dog food causing skin issues, but it is certainly possible. Beneful, or anything by Purina, is not a high quality food. Most high-quality, 3-5 star DFA rated foods do not contain artificial coloring, it is only the low-quality brands.