Facial Thermography Study of Levocetirizine Versus Cetirizine

Inclusion Criteria: * Healthy male Caucasian subject aged between 18 and 55 years (both inclusive). * Subject must have a positive prick test to histamine (wheal diameter ≥ 6 mm with histamine dihydrochloride (100 mg/mL) and ≤ 3 mm with diluent control). Exclusion Criteria: * History of allergic disease, documented or suspected, including but not limited to: asthma, whether or not considered as allergic; nocturnal cough episode suspected to be of asthma-equivalent nature (three or more consecutive nights resulting in sleep disturbances) ; allergic rhinitis, conjunctivitis or sinusitis; nasal polyposis; dermatitis of the face or neck; drug or food allergy. * Any clinically significant vascular disease such as hyper- or hypotension, venous disorder, vasculitis etc. * History of hot flushes and any other vasomotor disorders. * ENT infection or Upper Respiratory Tract Infection not completely cured at least one week before inclusion. * Any known history of laryngeal edema. * Nasal structural abnormalities (e.g. deviation of the nasal septum…). * Recent immunotherapy * Skin irritants or UV exposure 48 hours before each visit.