Mix equal parts vinegar, rubbing (isopropyl) alcohol, and water. A couple drops in each ear after showering or swimming can prevent "swimmer's ear" infections. It's also good to use in the ear canal of dogs with big, floppy ears who tend to get smelly, yeasty infections from playing in the water. Squirt in a generous amount and massage the ear area well, then let them shake it out. Just don't put it into ears that have an active infection when the dog has been scratching from the discomfort. They won't thank you.