Both are antihistamines. Here is how Zyrtec and Allegra compare on class, mechanism, dosing, approval and supply.
At a glance
ZyrtecCetirizine
AllegraFexofenadine
Brand names
Zyrtec / Reactine
Allegra / Telfast
Drug class
Second-generation antihistamine
Second-generation antihistamine
Route
Not listed
Not listed
Marketed by
Kenvue
Sanofi
First FDA approval
8 Dec 1995
25 Jul 1996
US shortage
Not listed
Not listed
Key differences
Same class. Both Zyrtec and Allegra are antihistamines, so they work through the same broad mechanism. Differences between them tend to be about dosing, route, how selective they are, and side effects rather than what they target.
Time on the market. Zyrtec was first approved by the FDA in 1995, Allegra in 1996.
Who markets them. Zyrtec is marketed by Kenvue; Allegra by Sanofi.
Same drug, more than one brand. Cetirizine is sold as Zyrtec / Reactine — the same active ingredient marketed under different brand names, typically for different approved uses or doses.
Same drug, more than one brand. Fexofenadine is sold as Allegra / Telfast — the same active ingredient marketed under different brand names, typically for different approved uses or doses.
This is not medical advice, and not a recommendation of one drug over the other.
Which medicine is right for a given person depends on their diagnosis, other conditions, other medicines, kidney and liver function, pregnancy, and cost or reimbursement — none of which this page knows. Two drugs in the same class are not automatically interchangeable. Never start, stop or switch a prescription medicine on the basis of a web page; that decision belongs to you and your clinician or pharmacist.
Class and summary text is written by the Priya Life Science editorial team. Label, mechanism, route, manufacturer and approval data come from the U.S. FDA via the openFDA API; shortage status from the FDA Drug Shortage Database. Approvals, indications and brand names differ between the US, EU/Ireland (EMA/HPRA) and other regions — a drug approved in one may not be approved, or may carry a different name, in another.
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