This is a placebo-controlled, 3-period crossover study to assess the efficacy and safety of two single doses of an intranasal anti-histamine GSK1004723 compared with placebo in an allergen challenge chamber in male subjects with seasonal allergic

Inclusion Criteria:

• Subject is healthy apart from seasonal allergic rhinitis, as determined by a physician. Can have mild asthma.
• Male
• Aged 18 - 65
• Weight 50kg+, BMI 19-32 kg/m2
• Exhibit response to Challenge Chamber and skin prick test.
• Non-smoker
• Capable of giving informed consent

Exclusion Criteria:

• No nasal structural abnornmality/polyposis, surgery, infection.
• any respiratory disease, other than mild asthma or seasonal allergic rhinitis
• participated in another clinical study within 30 days.
• Subject has donated a unit of blood within 1 month
• Use of prescription or non-prescription drugs, including vitamins and st john's wort within 7 days of trial.
• History of sensitivty to drug
• History of alcohol/drug abuse within 12 months.
• Positive Hepatitis B antibody test
• Positive HIV antibody test
• Risk of non-compliance with study protocol
• Perenial allergic rhinitis
• Administration of oral, injectable or dermal corticosteriods within 8 weeks, intranasal or inhaled within 3 weeks.
• Past or present disease that may affect outcome, as judge by investigator Specific Immunotherapy within 2 years