Swollen red skin

My 9 y/o fila has swollen red skin with silvery white (dead skin?) just below his anus and another area just suddenly developed around his belly button that looks the same (though less swollen). It should be noted he is on cipro and augmentin and prednisone (tapering down, currently 5mg) for discospondylitis among some other infections.   Is this moist dermatitis? Something from his stool and urine irritating his skin? 

Hello!  Moist dermatitis is usually oozing with pus, but you'd need to ask your vet to describe this skin for you.  The word 'Dermatitis' means 'inflammation of the skin' - its a description, not a diagnosis, and its likely appropriate here.  However I can't see any pus or exudate in the picture....   More To Follow

Never the less, there seems to be inflamed, thickened skin tracking down from the anus and this should be shown to a vet, as it may have faecal matter slide over it, which can make inflamed skin sore and infected.  It may need some kind of barrier cream / medicated shampoo, for example.  I wonder if the underside of the tail is also looking bald - it could be that demodex and underlying endocrine diseases might be involved, especially if the patient is on steroids, so more tests may be warranted.   Given the location and vulnerability of the skin, it is definitely worth bothering your vets with sooner rather than later.  They may be prepared to triage the case to establish its level priority.