The skin 'diseases' I've seen have all been linked to the spinal column. People talk about skin diseases as if it is from parasites. I think the parasites come after to feast on the waste produced by the body.
The body's electrical/nervous system is damaged and it shows up on the skin, not from parasites but from an inherited gene or some tendency which worsens its condition with age - like senility or pre-senility - the skin is just the location of the ends of those nerves degenerating. The darkened patches are the areas of influence of those dead nerves. See my "darkening" disease posts.:)
That's why these brain-spinal remedies are helping the animals. As their nervous system goes down, they grow more sensitive to the moon and to the weather, among other stresses. Fortunately homeopathy has remedies for most of these stresses, so I'm hopeful of reversing the problem for my babies across the species.
I really need to look into remedies specifically for nerve damage - something to heal nerves. Hypericum? Let me check.Kali phos 6 did some good in the dying Rocky who had huge patches of dead nerves, but it also brought out an aggravation. I need something that will do that kind of work but not aggravate too much.