Blisters A small bubble on the skin of feet filled with serum and caused by friction, burning, or other damage. New shoes and sports can cause friction which leads to blisters. Small and painful ﾖ blisters are a nightmare for everyone! Scholl Blister Shield Plasters To avoid infection, blisters should never come into contact with sand or dust. Cover them until they arecompletely healed, even if they no longer hurt.