This is handy to bookmark:
OTC Medications
Get a good joint supplement like Cosequin or Glycoflex. Most of the less expensive brands don't contain enough glucosamine to be effective. The chart posted shows the dosage for dogs under 25 pounds. My vet told me Lady needs 300 mg a day at 8 pounds. She also has arthritis and giving her Cosequin has made a big difference. It takes months to see an improvement, though, so be patient!
Adding a fish oil supplement can really help with allergies. I give Lady 3V caps.
Fatty Acids for Allergies & Dry Skin in Dogs