The purpose of this study is to see if the recruitment of a certain cell type (the alpha 4 integrin (CD49d) expressing neutrophil) during a nasal allergen challenge can be inhibited by pretreatment with an FDA approved leukotriene antagonist (montelukast).

Subjects will be consented, undergo skin testing, medical history questionnaires, and randomized to either placebo or montelukast (10 mg). In one week, subjects return, undergo a blood draw, medical history questionnaires, nasal lavage, and nasal allergen challenge (followed by lavage in 6 hours). Subjects will then cross-over to the other study drug. One week later subjects will undergo a blood draw, medical history questionnaires, lavage, allergen challenge, and repeat lavage (after 6 hours).

Inclusion Criteria:

• 21 - 65 years of age, inclusive
• A personal history of allergic rhinitis (hayfever) (by self-report)
• At least one positive skin test to cat, dust mite mix, Timothy grass, Bermuda grass, Bluegrass, or Ragweed
• Ability to provide informed consent
• Willingness to undergo epicutaneous skin testing
• Willingness to undergo nasal lavages and nasal allergen challenges
• Willingness to undergo 2 peripheral blood draws (10 cc each)

Exclusion Criteria:

• Use of systemic antihistamine in the past 5 days
• Use of intranasal corticosteroids or intranasal antihistamines currently or in the past 2 weeks
• Use of Montelukast currently or in the past week
• Hypersensitivity or allergy to Montelukast
• Inability to perform/undergo any study procedures
• Pregnancy (by subject report) or breastfeeding
• Confirmed or suspected immunodeficiency
• Persistent asthma, atopic dermatitis, or any other co-morbid disease except for allergic rhinitis
• Any symptoms of asthma in the past 2 weeks (shortness of breath, wheezing, and/or use of albuterol)
• Fever (temperature over 99F) currently or in the past 2 weeks
• Current or previous use of a biologic or investigational agent in the past 6 months
• Current or past suicidal thoughts/attempts