<prompt> Short acting anti-histamine is:CetirizinePromethazineHydroxyzineAcrivastine  <response>: Ans: B Promethazine Ref: Goodman Gilman s The Pharmacological Basis of Therapeutics, 12th ed, 2011, Pg 921-922.Explanation:Hydroxyzine, is a long acting first generation antihistamine used in the treatment of skin allergies. It acts for a duration of 6-24 hrs.Cetirizine a second generation antihistamine acts for 12-24 hrs.Acrivastine belongs to second generation antihistamine and acts for a duration of 6-8 hrs.Promethazine, a first generation antihistamine acts for a duration of 4-6 hrs.Among the first generation antihistamines longer acting drugs include doxepin 6-24 hrs, chlorpheniramine 24 hrs and meclizine 12-24 hrs . Of the 2nd generation antihistamines longer acting drugs are cetirizine 12-24 hrs. levocetirizine 12-24 hrs, azelastine 12-24 hrs. loratadine 24 hrs. desloratadine 24 hrs. ebastine 24 hrs, mizolastine 24 hrs, and fexofenadine 12-24 hrs. 