Thank you for your comments.
I suppose the posting (Allergy Tips) may explain your situation.
Cat allergy extracts are actually very well researched and tend to be very effective for most people. Unfortunately, when your cat skin test is negative, you will not qualify for the shots.
Its not so much how or where they collect the material from (hair, skin, dander etc.) as it is the sensitivity level of the test material used at the time.
I usually suggests, to patients that remain unconvinced of negative test findings, to come back for retesting in 1-2 years. Also, I do intradermal skin testing which are more sensitive at picking up allergy than skin ***** test or blood test. Many board certified allergist will proceed with selective intradermal (small injection just beneath the skin) skin testing after ***** test.
Finally, if you have other allergy triggers such as dust mite, pollens etc., being desenstized to them may have a beneficial outcome in your tolerance to cat dander.
Perhaps a re-visit to your allergist would be helpful.
Good Luck.