as moonlighter says could be from laying on bare boards or concrete, i have a dog here who likes to lay out in the run on the slabs, ive put pallets with carpet down for him but he just pisses up them and still lays on the slabs, he gets them on and off, i just ensure theres plenty of waxed paper on the bedboard. i think its fluid as if you massage twice daily it does help it go down quicker but as sadymere says this is all guess work without a photo to look at.