Fexofenadine HCl 180 mg, Montelukast Sodium 10 mg and Placebo in Suppression of Wheal and Flare Induced by Seasonal Allergen

Inclusion Criteria: * Male and female subjects, 15 to 55 years of age, may participate. * Subjects with a history of seasonal allergic rhinitis (due to ragweed; oak, elm or maple; or grasses) for the previous 2 years. * Positive seasonal allergen skin prick tests (or duplicate seasonal allergen skin prick test) with a summation flare greater than or equal to 20 mm larger than diluent control, and summation wheal greater than or equal to 6 mm larger than diluent control at the screening visit 1 (see Appendix 17.1); the seasonal allergen testing that results in the greatest summation flare will be used for all subsequent seasonal allergen testing. * 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. * 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. * Significant signs and symptoms of currently active allergic disease (SAR, 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 escalating doses of immunotherapy, oral immunotherapy or short course (rush) 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 history of chronic alcohol or mood-altering drug abuse. * 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. * Pregnancy. * Breast-feeding. * Regular treatment with other H1-receptor antagonists in the last year before study entry. * No person or child of a person directly associated with the administration of the study may participate as a study subject. * Likelihood of requiring treatment during the study period with drugs not permitted by the clinical study protocol. * Treatment with any investigational product in the last 30 days before study entry. * 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: Systemic or injected corticosteroids (including oral, parenteral, intravenous, rectal) 30 days; Nasal or inhaled or ocular corticosteroids 30 days; Nasal or inhaled ipratropium bromide (or atropine), inhaled nedocromil, or nasal, inhaled, or ophthalmic sodium cromolyn 14 days; Agents with antihistaminic/anticholinergic activity (e.g. antidepressants, antipsychotics) 14 days; Leukotriene pathway modifiers (Accolate, Singulair, Zyflo) 10 days; Ocular anti-allergy medications including lodoxamide (Alomide), olopatadine (Patanol), emedastine difumarate (Emadine), levocabastine (Livostin) 10 days; Non-steroidal anti-inflammatory ophthalmics including ketorolac (Acular), flurbiprofen (Ocufen), suprofen (Profenal), diclofenac (Voltaren) 10 days; Antihistamines including desloratadine (Clarinex), loratadine (Claritin) 10 days; Antihistamines including fexofenadine HCl (Allegra), cetirizine (Zyrtec), hydroxyzine, azelastine nasal spray (Astelin), clemastine 7 days; Other short-acting antihistamines such as chlorpheniramine or drugs with antihistaminic activity 3 days; OTC oral antihistamines, decongestants (includes pseudoephedrine and other decongestants), or antihistamines/decongestant combinations including all cold, cough, and sleep aids 3 days; OTC ophthalmic decongestant,antihistamine, or decongestant/antihistamine combinations 3 days; Other anticholinergic agents 3 days; Immunotherapy injection 1 day. * Other drugs should only be permitted if they are not expected to interfere with the ability of the subject to participate in the study. * Non-steroidal anti-inflammatory agents are not allowed for 2 days prior to each treatment visit day through 25 hours post-dose (low-dose cardiac prophylaxis is allowed). * Use of any medications or agents that are not specified above that may confound the interpretation of the results: * Caffeine within 6 hours prior to each visit (coffee, tea, cola, and sodas, including Mountain Dew and Surge) * Decaffeinated coffee, tea and colas within 6 hours of each visit * Alcohol within 24 hours prior to each study visit * Chocolate within 6 hours prior to each visit * Antacids within +/- minus2 hours of investigational product dosing.