Desloratadine is an active, descarboethoxy metabolite of loratadine. It acts by selective inhibition of H1 histamine receptor and thus provides relief to patients with allergic rhinitis and chronic idiopathic urticaria. Desloratadine was approved by FDA and it is currently marketed under the name Clarinex (among the others).

Fexofenadine is a second-generation, long lasting H1-receptor antagonist (antihistamine) which has a selective and peripheral H1-antagonist action. Histamine is a chemical that causes many of the signs that are part of allergic reactions, such as the swelling of tissues. Histamine is released from histamine-storing cells (mast cells) and attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cell to be "activated," releasing other chemicals which produce the effects that we associate with allergy. Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of cells by histamine. Unlike most other antihistamines, Fexofenadine does not enter the brain from the blood and, therefore, does not cause drowsiness. Fexofenadine lacks the cardiotoxic potential of terfenadine, since it does not block the potassium channel involved in repolarization of cardiac cells. Fexofenadine is sold under the trade name Allegra among others. ALLEGRA is indicated for the relief of symptoms associated with seasonal allergic rhinitis in adults and children 2 years of age and older.

Levocetirizine is the active enantiomer of cetirizine. It is inverse agonist of H1 receptors. Levocetirizine hydrochloride was approved for treatment of Allergic Rhinitis and Chronic Idiopathic Urticaria.

Mizolastine (Mizollen) is a long-acting H1 -antihistamine indicated for the symptomatic relief of seasonal allergic rhinoconjunctivitis (hay fever), perennial allergic rhinoconjunctivitis and urticaria. It blocks H1 receptors and is commonly fast-acting. It does not prevent the actual release of histamine from mast cells, just prevents it binding to receptors. Side effects can include dry mouth and throat