Hello and hope you are doing well.
Zyrtec can cause side effects like skin nodules, rash, pruritis (itching), acne, urticaria, photosensitivity reactions and eczema. So, the itchy red cheeks could be due to Zyrtec. Discuss your symptoms with your consulting doctor he may change the dose or the medications.
Hope this helped and do keep us posted.
there's a possibility that you may be sensative to it i am highly allergic to flonase and naselnex allergy medicines