Safety Study of Levocetirizine Dihydrochloride Oral Liquid Formulation in Children Aged 1 to Less Than 6 Years Suffering From Allergic Rhinitis or Chronic Urticaria of Unknown Origin

Inclusion Criteria: * Outpatient, male or female pediatric subject, ages 1 to less than 6 years old at the Randomization Visit (V2) (1 - \< 6 years old) * The subject must present at least one of the following symptoms, most commonly associated with allergic rhinitis or chronic urticaria: nasal itching, sneezing, rhinorrhea, nasal congestion, tearing, eye redness and itching of eyes, ears and/or palate, skin wheals and itching of the skin * Subjects (age 2 to less than 6 years only) suffering from allergic rhinitis (AR) should have a documented allergy measured by positive skin prick test or RAST (Radioallergosorbent Test) performed within the last 6 months prior to randomization * Candidate for antihistamine treatment or received antihistamine in the past for similar symptoms as those presenting * Caregiver(s) have been informed of the nature and aims of the study and have given their written informed consent for the subject to participate in this study * Caregiver(s) able to understand information given, the text of the informed consent, and be able to complete the daily record card (DRC) Exclusion Criteria: * Any clinically significant medical condition or abnormality other than the primary diagnosis for which an antihistamine is indicated * Be initiating or changing the dose of an immunotherapy regimen during the course of the study (Visit 1 to Visit 4) * Any electrocardiogram (ECG) parameters, including a QTcF interval \> 443 msec measured by an ECG obtained at the Screening Visit, outside the normal reference ranges * Any clinical laboratory tests performed at the Screening Visit, other than those related with the allergic condition, outside the reference ranges. Subjects having values outside the accepted reference range can be included if in the Investigator's opinion, they are of no clinical significance * Personal history of seizure, febrile seizure or sleep apnea * Below the lower 5th or above 95th percentile for body weight and/or height based upon CDC Growth Charts for Body Weight and Length * Allergy or intolerance to levocetirizine dihydrochloride or its excipients, or to any other piperazine derivatives, such as hydroxyzine, cetirizine, cyclizine, meclozine, buclizine * Current or past intake of the following medications (including exposure through breast milk) within the specified wash-out period before the Randomization Visit (V2): 1. Systemic corticosteroids within the past 28 days 2. Leukotriene-receptor antagonists (e.g. montelukast \[Singulair\] or zafirlukast \[Accolate\] within the past 7 days) 3. Mast-cell stabilizers (e.g. cromolyn or nedocromil) within the past 7 days 4. Other antihistamines or cough and cold preparations (with the exception of single ingredient guaifenesin products) or over-the-counter (OTC) sleep aid medications within the past 7 days 5. Systemic antibiotics within the past 7 days 6. Other concomitant medications that will interfere with the study, in the opinion of the investigator * Previous participation in another clinical/pharmacological trial within the past month prior to V1 * Have already participated in this study or participated in this study at another site * Children of any member of the study site staff