Outer influence — environment. Wet and mud change the conditions for the skin.
The skin softens. Healthy skin has a tight outer layer that keeps microbes out. Under prolonged wet and moisture that layer swells and softens — the cells drift apart, the surface turns porous and the barrier weakens.
Bacteria gain a foothold. Mud, manure and urine are full of bacteria, and softened, moist skin is exactly the breeding ground they need.
The environment keeps it going. Packed mud shuts out the air and creates an oxygen-poor, moist environment against the skin. As long as the skin stays wet and dirty, the cycle continues.
Inner influence. Skin and hooves also mirror what happens inside the horse. An imbalance in the gut can impair uptake of the nutrients the skin and horn need — so sometimes you also need to review feed and gut health.