Dogs ear is red

Question
Dear Dr. Gotthelf,

My dog, (he's a one year old Goldie) has a red ear.  Can I give him an old dose of Betagen Otic Solution?  It's about 3 years old.  I've had it in the refrigerator.

Thanks,  

Earl

Answer
The Betagen is probably still good and it does have a very potent steroid in it, but without knowing why the ear is red, that may be a very short term fix.  If there is an allergy, then it will help for a few days.  If there is a yeast infection, it will help the itching, but the yeast will not be treated by the gentamycin in the Betagen.