May see loss of hearing or balance. These effects are usually temporary. If ingested, the most common side effect of corticosteroids is an increase in the amount of drinking and urinating. Less common side effects are an increased appetite and weight gain, panting, diarrhea, vomiting, and behavior changes. If your pet experiences an allergic reaction to the medication, signs may include facial swelling, hives, scratching, a sudden onset of diarrhea, vomiting, shock, seizures, pale gums, cold limbs, or coma.