Fexofenadine HCl 180 mg, Desloratadine 5 mg and Placebo in Suppression of Wheal and Flare Induced by Histamine

Inclusion Criteria: * Male and female subjects, 12 to 55 years of age, may participate * Positive histamine skin prick tests (or duplicate histamine skin prick test) with a summation flare (ΣF) greater than or equal to 20 mm larger than diluent control, and summation wheal (ΣW) greater than or equal to 6 mm larger than diluent control at the screening visit 1 * All female subjects must have a negative urine pregnancy test at the screening visit * Female subjects who are sexually active will be expected to use one of the following birth control methods throughout the study (see Section 4.4) * Subjects must be within 15% of normal body weight for height or a BMI less than 29.9 (based on NHLBI guidelines) * Subjects willing and able to adhere to visit schedules and all study requirements * All female subjects must have a negative urine pregnancy test at each treatment visit (Visit 2, 4, and 6). * Continues to meet all inclusion and exclusion criteria Exclusion Criteria: * Asthma that requires treatment with medication other than an inhaled, short-acting beta agonist * Signs and symptoms of currently active allergic disease (seasonal allergic rhinitis, perennial allergic rhinitis, episodic allergic rhinitis) * Upper respiratory tract infection, sinusitis, asthma or flu-like symptoms within 2 weeks prior to visit 1 * Subjects who have dermatographism or other skin conditions which might interfere with the interpretation of the skin test results * Subjects who are receiving immunotherapy * Any excessive amounts of alcohol (no more than two drinks/day on average) * Any excessive use of caffeine (more than six cups of coffee per day or equivalent) * Any use of tobacco/nicotine products within 90 days of visit 1 * Any disease state or surgery known to affect the gastrointestinal absorption of drugs * Known hypersensitivity to the investigational product or to drugs with similar chemical properties * Subjects who will be visiting a tanning salon during the study * Subjects who will need to use artificial tanning products during the study * Night or variable shift workers during the study * Pregnancy * Breast-feeding * History of hypersensitivity to the study medications or to drugs with similar chemical structures * Treatment with other H1-receptor antagonists in the last year before study entry * Likelihood of requiring treatment during the study period with drugs not permitted by the clinical study protocol (see Section 6.2) * Treatment with any investigational product in the last 30 days before study entry * No person or child of a person directly associated with the administration of the study may participate as a study subject * Clinically relevant cardiovascular, hepatic, neurologic, endocrine, or other major systemic disease making implementation of the protocol or interpretation of the study results difficult * Mental condition rendering the subject unable to understand the nature, scope, and possible consequences of the study * Subject unlikely to comply with protocol, e.g., uncooperative attitude, inability to return for follow-up visits, and unlikelihood of completing the study * Use of any of the following drugs within the time indicated prior to the first dosing visit: