My dog keeps shaking his head, his ear smells and there's brown gunk — can I just buy ear drops?

No — please don't put anything in that ear until a vet has looked inside it, and here is the honest reason why.

The vet needs to see the eardrum. If it is already damaged — and a painful, infected ear is exactly where that happens — then some cleaners and some drops that are perfectly safe in an intact ear can harm hearing and balance once they reach the middle ear. That is not a theoretical risk. It is also why a product chosen off a shelf is a gamble that isn't yours to take.

The second reason is the swab. Yeast and bacteria look identical from the outside — brown gunk and a smell tell you nothing about which one it is — and they are treated with completely different medications. A drop of that discharge under a microscope answers it in minutes. Guessing wrong means more weeks of a painful ear and a more stubborn infection.

So: don't clean the ear for the 24 hours before the appointment, because you would be washing away the very sample the vet needs. Note which ear it is and how long this has been going on. Photograph the discharge. And no cotton buds, ever — they push debris down towards the drum.

One more thing worth hearing. Ears that get infected again and again are usually not really an ear problem; they are the visible end of an underlying allergy. Treat the ear and ignore the driver, and you will be back in six weeks. Ask your vet directly whether that is what is going on with him.

Go sooner rather than later if you see a head tilt, loss of balance, eyes flicking from side to side, or he screams when the ear is touched.