Claritin Vs. Zyrtec: Which Is More Effective?

In our latest question and answer, the pharmacist compares Claritin (loratadine) and Zyrtec (cetirizine) in regard to which one works better for treating allergy symptoms.

Claritin Vs. Zyrtec: Which Is More Effective?
Apr 06, 2018

SammyJane asked

I know that it can be difficult to parse differences between antihistamines but I am wondering if there are actual studies that compare Claritin and Zyrtec in terms of how EFFECTIVE they are for allergies. I know Zyrtec can cause drowsiness but I am wondering if there is DATA on how well they work to reduce allergy symptoms and if one is more effective.


Claritin Vs. Zyrtec EffectivenessThere are many studies that have compared the effectiveness of Claritin (loratadine) and Zyrtec (cetirizine).  Zyrtec has been shown to be more effective than Claritin for reducing allergy symptoms. However, Zyrtec causes significantly more drowsiness than Claritin.

Zyrtec Vs. Claritin: What The Studies Say

One study reviewed and combined data from 13 previously done studies to compare the effectiveness of allergy medications including Claritin and Zyrtec.  The study included 6,867 patients with allergic rhinitis (seasonal allergies) and gauged effectiveness by reviewing the patient’s answers to a standard survey about their symptoms. 

  • The results showed that Zyrtec was the most effective medication for allergic rhinitis (i.e. allergy symptoms) and 26% more effective than Claritin.  
  • However, as mentioned above, the study noted that Zyrtec causes significantly more sedation and drowsiness than Claritin.

Another study tested which medication works faster to reduce allergy symptoms and which is more effective.  It included 120 patients with allergic rhinitis and exposed them to allergens like pollen to see when the allergy medicine started working.

  • The results showed that Zyrtec started working 2 hours sooner than Claritin and Zyrtec was about 14% more effective than Claritin in reducing symptoms.  

Several other studies showed similar results and we couldn't find any studies that showed Claritin is more effective than Zyrtec (All studies reviewed showed that Zyrtec was either more effective than Clariitn or no difference between the two could be shown).


  • Claritin and Zyrtec are both effective drugs to relieve allergy symptoms.
  • However, Zyrtec has been shown to be more effective and work more quickly than Claritin in several studies.
  • Zyrtec does cause more drowsiness than Claritin. Drowsiness occurs in about 22% of people who take Zyrtec compared to 2-4% in those who take Claritin.

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