I am sorry to hear that the pup you are looking after is shaking her head and scratching and may have an ear infection.
Generally dogs with an ear infection have increased amounts of waxy debris in their ear(s), their ear is red, has an odor and the canal may be swollen.
Of course the ideal situation if she has any signs of an infection is to have her see her veterinarian and have her ear debris tested to see what sort of infection she has to get her on the right medication, but I understand that may not be possible immediately given it is the weekend.
In the meantime there are some things that we can do to help her feel more comfortable.
Since most ear infections are secondary to allergies and the inflammation they cause you can use a combination of antihistamines and high doses of omega-3 fatty acids to help with those. In combination fatty acids and antihistamines work synergistically, much better than either one alone.
You can try:
1)Benadryl (diphenhydramine only don't use the combination products with decongestants or acetaminophen as they can be toxic) at 1mg to 2mg per pound or one 25mg capsule per 15 to 25 pounds of body weight orally every 8 hours.
OR 2)Claritin (loratidine) at 5mg per 25 pounds of body weight once or twice daily.
OR 3)Hydroxyzine at 1mg per pound of body weight orally every 8 hours.
OR 4) Chlorpheniramine at 4mg to 8mg per dog once or twice daily.
OR 5) Zyrtec (Cetirizine hydrochloride) at 1/2 mg per pound of body weight orally every 24 hours. That would be one 10mg tablet per 20 pounds of body weight. Make sure it is NOT the formulation with a decongestant (such as Zyrtec-D) because dogs cannot tolerate decongestants.
Some dogs do better on one antihistamine rather than another. Give the one you pick a 3-5 day trial and if she isn't more comfortable try another. Be aware that antihistamines can cause sleepiness or hyperactivity in some dogs. These side effects do wear off with repeated use.
Omega-3 fatty acids are fish oil products. Welactin is a good brand name product. Use the high end of the dosing schedule for your pup's weight. I recommend an omega 3 fatty acid dose based upon the EPA portion (eicosapentanoic acid) of the supplement as if we do that the rest of the supplement will be properly balanced. Give her 20mg of EPA per pound of body weight per day. For example an 80 pound dog could take 1600mg of EPA per day.
I also recommend using a gentle ear cleaner like Oticlens daily now to remove as much of the water and waxy debris as possible. This removes excess wax and keeps the ear pH at levels that discourage infections. When the ear is sore many dogs won't let you squirt things in their ear but if you soak a cotton ball with the cleaner, then place it at the top of the ear canal and massage the ear from the outside, putting pressure on the soaked cotton ball, the cleaner will be instilled easily. Wipe out excess cleaner and waxy debris with dry cotton balls.
Once you have her infection treated and cleared use the cleaner twice a week as that helps prevent infections and also allows you to know what a normal ear looks like and catch ear infections very early.
Sometimes with an early infection simply cleaning the ear daily is enough to stop it in its tracks.
If her ear skin surface is very red after cleaning you can apply a light coat of hydrocortisone cream (like Cortaid) to the ear skin with a cotton ball.
Do not clean her ear the day of her veterinary appointment so they can gather a sample of the wax for testing.
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