I have to step away from the computer for a number of hours, but wanted to leave you with additional information based on what you have already told me before I go.
What you are describing certainly sounds like an ear infection. This may be the common type called Otitis Externa, or (if you just adopted him) it could be caused by mites. These are very rare in dogs and I have only seen them in dogs that have very low immune systems caused by living on the streets. The other thing that I would consider is that there could be a foreign body in the ear, such as a grass awn if you live in an area where such things are growing at this time of year.
Ear infections (otitis externa) are quite common. There may be an underlying allergy that is making your dog prone to these. We start to wonder about allergies when we see repeat ear infections in a patient. Allergies can be to something inhaled (then we call the allergy "atopy") or to something eaten (usually a protein - it could be anything from chicken to beef to lamb or ANY other protein that the dog has ever eaten).
In the case of food allergy, we usually recommend a food with a NOVEL protein that the dog has never had before (venison, fish, duck, rabbit are all options) and NO other sources of protein. That means NO treats, NO rawhides, NO table scraps.
In the case of atopy, we often have to manage the condition with antihistamines, omega 3/6 essential fatty acids and sometimes corticosteroids.
Otitis externa is commonly caused by yeast, bacteria or a combination of both. Quite often, the ear medications that I prescribe have a combination of anti-fungals to treat the yeast, anti-biotics to treat the bacteria and anti-inflammatories to decrease the pain and inflammation. The names of a couple of ear medications I commonly prescribe are Surolan and Otomax.
In terms of what you can do at home without seeing a vet, you could try:
1. Burrow's Solution (Buro-sol, http://www.feelbest.com/Pages/ItemDetails.aspx?GroupID=EADRO&TYPE=FINE&LINKPAGE=ItemDetails.aspx&ID=05546000017
In Canada, you can get Burrow's Solution over the counter at a pharmacy. I believe it is widely available in the USA as well. It is a gentle astringent that is very useful in treating ear infections. Many veterinarians carry it, compounded with 2% hydrocortisone (for that you would need a prescription). But you could certainly try it twice daily for 7 days in your dog. Instill 3-5 drops into both ears twice daily for a week.
2. You could start your dog on Essential Fatty Acids, orally. These decrease inflammation in the body and are very helpful with skin, hair and ear issues. EFA-Z and DermCaps are a couple of brands. It takes 8 weeks to see improvement.
3. Antihistamines - you could try hydroxyzine or chlorpheniramine since atopy could possibly be part of the problem with your dog.
Oral antibiotics are rarely needed to treat ear infections, as the drug doesn't get to the site of the infection effectively. When you give an oral antibiotic, it ends up in the blood stream, and this is not helpful for treating ear infections which are on the skin surface within the ear. Occasionally I use oral antibiotics if there are signs of an INNER ear infection. This is rare.
Here are some links about Otitis Externa that you might find useful:
Given that your vet's office is likely to be closed for the holidays, it would be prudent to have him seen today or tomorrow so you have prescription medication for his ears to ensure they improve quickly and that you do not end up seeing an emergency clinic over Christmas to treat this.
I hope that your dog feels better soon!
Good luck with your dog. If this has been helpful, please hit the green "Accept" button.
If you need more information, just click on reply and I will still be back to provide it!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would strongly advise contacting your regular veterinarian.