My son's pediatrician did the serum testing as he doesn't like to do the scratch test on young children because it is uncomfortable for them.
He has us give Aiden Claritin when it is a season where his allergies affect him, which works well for him. It just might me the Zyrtec that is the problem, not all allergy medications are effective on all people. Claritin and Zyrtec do NOTHING for me, only Benadryl, Dimetapp, and Singulair have ever seemed to help, but Claritin is great for my son. If the Zyrtec doesn't seem to help much, ask if you can try something different.