• PK parameters and plasma concentrations of SCH 34117 (the active metabolite) between the 3 age groups (3-6 years old, 7-15 years old, and 16-64 years old). [ Time Frame: after 1, 2, 3, and 4 weeks of treatment. ] [ Designated as safety issue: No ]
• Change from baseline in score of 4 nasal symptoms [ Time Frame: after 2 and 4 weeks of treatment ] [ Designated as safety issue: No ]
• Incidence of adverse drug reactions. [ Time Frame: from start to end of treatment (after 4 weeks of treatment) ] [ Designated as safety issue: Yes ]

This is a post marketing study to confirm the appropriate dose of loratadine in children by obtaining drug concentration data at multiple time points per child and adult patient, after the patient receives repeated administrations of the approved dose of loratadine.

• Experimental: Pediatrics 3 to 6 years
• Experimental: Pediatrics 7 to 15 years
• Experimental: Adults 16 to 64 years

Inclusion Criteria:

• Patients with confirmed diagnosis of perennial allergic rhinitis, between the ages of 3 and 64 years of age, outpatients of either sex, patients with appropriate written informed consent and ability to perform the tasks required for the study, patients for whom treatment with loratadine is appropriate based on symptoms of perennial allergic rhinitis

Exclusion Criteria:

• Patients with history of epileptic seizures or organic brain dysfunction in whom there is a possibility that epileptic seizures may be induced, patients with a history of hypersensitivity to the drug or component of the drug, patients who are pregnant, nursing or intending to become pregnant, patients with severe hepatic, renal, cardiac, or hematological disease or other serious complications or poor condition, patients participating in another clinical study within the past 30 days, patients otherwise judged inappropriate by the investigator.