Why Does Generic Zyrtec Not Work?

Because non prescription products are regulated differently to prescription medicines FDA equivalence ratings are not assigned to generic Zyrtec products. Therefore, it is difficult to say with certainty that a "generic" non prescription medication is completely equivalent to the brand-name product.

Does generic Zyrtec work as well as Zyrtec?

No. Generic medications are just as effective as brand-name drugs.

Is generic Zyrtec effective?

Cetirizine (Zyrtec) is available as a generic medication and may be significantly cheaper compared to the brand version. Unless there is a specific reason you need the brand, the generic medication will be a better value.