Evaluation of Nasal Inflammatory Biomarkers

Inclusion Criteria: 1. Able and willing to give written informed consent. 2. Male or female, age 18-65 years. Women will be considered for inclusion if they are: * Not pregnant, as confirmed by pregnancy test, and not nursing. * Of non-child bearing potential (i.e. physiologically incapable of becoming pregnant, including any female who is pre-menarchal, or post-menopausal with documented proof of hysterectomy or tubal ligation, or meets clinical criteria for menopause and has been amenorrhoeic for more than 1 year prior to the screening visit). * Of childbearing potential and using a highly effective method of contraception during the entire study, as defined by at least one of the following * vasectomised partner * sexual abstinence (the lifestyle of the female should be such that there is complete abstinence from intercourse from two weeks prior to Visit 2 procedures until at least 72 hours after NAC) * implants, injectables, combined oral contraceptives, hormonal IUDs or double-barrier methods (i.e. any double combination of IUD, condom with spermicidal gel, diaphragm, sponge, and cervical cap) 3. History of seasonal allergic rhinitis to grass pollen with symptoms during the 2016 and 2017 allergen season requiring treatment with anti-histamines, nasal corticosteroids or leukotriene antagonists. 4. Absence of significant current symptoms of allergic rhinitis consistent with being out of season for their principal allergen (eg grass). 5. Skin prick test positive for mixed grass pollen allergen at Visit 1 or within one year prior to screening. Exclusion criteria 1. Asthma requiring more than inhaled short-acting beta-2 agonists. 2. Spirometry showing FEV1 \<80% predicted 3. Subjects who have smoked more than 5 cigarettes in the last 6 months or have a smoking history of ≥10 pack years. 4. Upper or lower respiratory tract infection in the prior 4 weeks. 5. Nasal or lung provocation procedure (eg, allergen challenge) conducted in the prior 4 weeks. 6. Significant nasal deformity, recent nasal surgery or obstructing nasal polyps. 7. History of anaphylaxis (any cause), or previous severe hypersensitivity reaction to any of the test agents for SPT or NAC. 8. Recent participation in a study of an investigational medicinal product (IMP) which could interfere with markers evaluated in this research 9. Use of any medications according to section 5.2 in the period indicated before Visit 1