Zyrtec vs Allegra: side-by-side comparison
Zyrtec (Cetirizine) and Allegra (Fexofenadine) both belong to the Allergy and Antihistamines class. They share clinical context but use different active ingredients. The choice between them depends on mechanism nuances, side-effect profile and individual response.
| Property | Zyrtec | Allegra |
|---|---|---|
| Active ingredient | Cetirizine | Fexofenadine |
| Manufacturer | Johnson & Johnson | Sanofi |
| Class | Allergy and Antihistamines | Allergy and Antihistamines |
| Strengths | 5mg, 10mg | 30mg, 60mg, 120mg, 180mg |
| Forms | tablet, oral solution, orodispersible tablet | tablet, oral suspension, orodispersible tablet |
What's the same
Zyrtec and Allegra both belong to the Allergy and Antihistamines class and are used for partially overlapping indications. The active ingredients — Cetirizine vs Fexofenadine — share the same therapeutic approach, so many safety and management points carry across both.
Key differences
Meaningful differences are in active ingredient (Cetirizine vs Fexofenadine), strengths (5mg, 10mg vs 30mg, 60mg, 120mg, 180mg), forms (tablet, oral solution, orodispersible tablet vs tablet, oral suspension, orodispersible tablet), and the mechanism, half-life and side-effect nuances that distinguish members of the class.
Mechanism and action
Zyrtec: Cetirizine selectively blocks peripheral H1 histamine receptors, antagonising the effects of histamine released by mast cells during allergic responses. Allegra: Fexofenadine selectively blocks peripheral H1 histamine receptors, antagonising the effects of histamine on vasodilation, capillary permeability, sensory nerve endings and smooth muscle.
When Zyrtec is preferred
Zyrtec is approved in adults and children for the treatment of seasonal and perennial allergic rhinitis, allergic conjunctivitis and chronic idiopathic urticaria.
When Allegra is preferred
Allegra is approved in adults and children for the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria.
Frequently asked questions
Is Zyrtec or Allegra better? ▾
There is no single answer. Zyrtec and Allegra both belong to the Allergy and Antihistamines class but differ in mechanism nuances, half-life and side-effect profile. Preference depends on the patient, the prescriber and prior response to other therapies.
Can I switch from Zyrtec to Allegra? ▾
Switching within the Allergy and Antihistamines class is done under supervision, typically using equivalent doses and a follow-up period to confirm response and tolerance. It is not a self-directed decision.
Do Zyrtec and Allegra have the same side effects? ▾
They share many of the Allergy and Antihistamines class side effects, with differences from mechanism and dose. Each medication's prescribing information lists specifics.
More Zyrtec comparisons
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.