What is the Strongest over-the-Counter Allergy Medicine?

Cetirizine (Zyrtec) and fexofenadine (Allegra) are considered the strongest over-the-counter antihistamines available. Both are second-generation antihistamines that provide 24-hour relief with minimal drowsiness. Clinical studies show cetirizine blocks 90% of histamine activity within one hour, while fexofenadine offers comparable efficacy with zero sedation risk. For nasal congestion, combining these with pseudoephedrine creates the most potent OTC allergy relief. Loratadine (Claritin) is slightly weaker but remains effective for mild to moderate symptoms. The "strongest" choice depends on your specific symptoms and tolerance for potential side effects like mild drowsiness with cetirizine.