It may be possible that she is having an allergic response to something. In this case you can give her benedryl at a dose of 1mg per pound. However, looking into the ears without special instrumentation does not rule out an inner ear infection. Most times the infection is much deeper within the ear then the naked eye can see. If the head shaking continues then a trip to the vet would be recommended check the ear and start antibiotics if infection is present.
Theresa
Preferably you should go to the store and pick up the benedryl. If not there are a couple of other antihistamines but you would need to let me know what you have:
hydroxyzine (atarax)
chlorpheniramine (chlortrimeton)
zyrtec
claritin
The dosage is 1mg per pound up to three times daily. At least twice should help if this is caused by allergies or an allergic reaction.
A Voice for Your Pet
15 years experience in small animal medicine