
Hi Gabrieldobe,
My Munsterlander had it a couple of times, where an infection entered a crack on her elbow, the whole leg swelled up and oozed a sticky substance, I presume your Dobe does the same, the oozing is from the infected skin.
Do not know how to avoid it occurring, but it would not hurt to wash the feet in a diluted hibiscrub solution, we use that for pyoderma on the chins of young Flatcoats and it clears the pustules up.