Compare the activity of 5 mg levocetirizine and 5 mg desloratadine on allergen-induced wheal and flare reaction.

Inclusion Criteria:

• Male and female allergic volunteers: Diagnosed allergy based on medical history and on positivity to skin tests to at least one of the standardized allergen including grass pollens, tree pollens, house dust mites, cat and dog dander and with a positive RAST for the specific selected allergen ≥ class 2

Exclusion Criteria:

• Pregnancy or lactating females, or females with childbearing potential without reliable contraception
• History or presence of any chronic or acute illness or disorder capable of altering the absorption, metabolism or elimination of drugs, or constituting a risk factor when taking the trial medication
• Heavy caffeine drinker (> 5 cups of coffee, tea, cola, etc … per day)
• Any drug treatment, including prescribed or non-prescription medicines (except hormonal contraceptives or post-menopausal hormonal replacement therapy for females and occasional use of paracetamol not exceeding 2 g/day with a maximum dose of 10 g per 14 days), taken from 14 days before study drug administration; the wash-out period after intake of systemic corticosteroids is at least 4 weeks
• Known allergy/intolerance to the study drug or any medicine chemically related to study drug or its excipients (lactose, cellulose...)
• Participation in another clinical trial, blood donation or significant blood loss (> 450 mL) less than 12 weeks before the study drug administration
• Skin irritant or 48 hours UV exposure before each visit
• Immunotherapy received during the current year
• Any clinical conditions that, in the opinion of the Investigator, would make the subject unsuitable for the trial