As Konnie said, her vet recommended this. Important point! This is a good, old-fashioned remedy for the beginning of a mild recurring ear problem.
But please do NOT use OTC remedies for what you suspect is an ear infection without specific vet recommendation, or experience of your own. Get vet advice, as Konnie says.
Ear infections come in all types, and spending time with an OTC remedy in the case of a serious bacterial infection can result in not just severe pain to the dog, but, as Nancy says, destruction of the ear canals.
I rescued a dog in the 90s who was deaf from repeated ear infections. These were a combination of bacteria and yeast (common), and, as Nancy says, required a broad-spectrum antibiotic to clear up the one she was enduring when she came to me and then treatment for the 30+ severe allergies she tested with (and which were triggering the ear infections).
I'm all for OTC remedies, and very much in agreement that we overuse and misuse antibiotics, but serious ear infections can be one of the places where antibiotics are godsends.
I also want to mention that alcohol in an inflamed inner ear with possibly broken skin or punctures from claw-swipes would be much worse than painful.
I examine my dogs' ear regularly (especially the GSD's ears) and am alert to even the beginnings of inflammation. Then, when I see the beginnings of one (either inflammation or debris, or both), I start home treatment immediately.
BUT this is for just the beginnings of a problem, and it's also for dogs whose ears I've become very familiar with. Also, by now I can smell or see the difference between most ear problems (yeast, bacteria, mites, etc.). Even so, I can't tell when there's a combination of problems, which is very common, and which requires the vet's microscope (at least) to sort out.
I'd recommend that if it's a dog's first ear problem, we always see the vet. Leaving a bacterial infection untreated can really present problems down the road, including escalation from simple antibiotics to aggressive broad-spectrum antibiotics and even antibiotic-resistant bacteria. (This last is definitely not a common outcome, but a local rescue group put down a dog two years ago after trying to save her with IV antibiotic therapy in the hospital; she had an ear infection that had turned gangrenous and killed tissue from her ear down the side of her head and jaw and into her upper shoulder.)
Because I have rescued several dogs with allergies, I've met a lot of ear infections. I've learned to respect them and to watch for them diligently, especially with any dog who has allergies.
Thank you both! I'm glad you brought this up. This problem comes up more and more as canine allergies become more and more prevalent.

And GSD's, even with their upright ears, are one of the ear-infection-prone breeds.