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Allegra and Claritin belong to the newer antihistamines, called second generation antihistamines, cause much less sedation and act longer than the antihistamines of earlier generations. Allegra, Clarinex, Claritin, and Zyrtec are taken orally. Some other antihistamines are available as nasal spray. This can lead to the cases when a person does not tolerate it as the antihistamine medications taken orally.
There were only few studies comparing antihistamines of second generation. Thus it is very difficult to compare the effectiveness of Claritin and Allegra. One can hardly determine if one is superior to the other in controlling allergy symptoms. The American Academy of Allergy, Asthma, and Immunology (AAAAI) clinical practice guidelines for allergic rhinitis admits that although the studies of second generation antihistamines are limited it appears that total clinical effectiveness and patient acceptance of Allegra and Claritin is almost the same.
Basically many specialists believe that all antihistamines have almost the same effectiveness. They can only differ according to the acceptance of the patient.
One of the differences between Claritin and Allegra is that Calritin can be dosed once daily whereas Allegra is dosed once or twice daily.
According to the data presented today at the annual American College of Asthma, Allergy and Immunology (ACAAI) meeting showed that in a wheal and flare suppression test single-dose Allegra 180 mg exhibits significantly faster onset of action in patients and is more effective in wheal and flare suppression compared to Claritin 10 mg.