Inclusion Criteria:

• Outpatient, male or female pediatric subject, aged from 6 to 11 months (6 months - < 1 year) at the randomization visit.
• The subject must present at least one symptom most commonly associated with allergic rhinitis or chronic idiopathic urticaria.
• Candidate for antihistamine treatment or received antihistamine in the past for similar symptoms as those presenting.

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 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 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 (including exposure through breast milk) of the following medications within the specified wash-out period before the Randomization Visit (V2):

  • Systemic corticosteroids within the past 28 days.
  • Leukotriene-receptor antagonists (e.g. montelukast [Singulair] or zafirlukast [Accolate] within the past 7 days).
  • Mast-cell stabilizers (e.g. cromolyn or nedocromil) within the past 7 days
  • Other antihistamines or cough and cold preparations (with the exception of single ingredient guaifenesin products), or OTC sleep aid medications within the past 7 days.
  • Systemic antibiotics within the past 7 days.
  • 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.
• Sibling with sleep apnea or sudden infant death syndrome (SIDS).

• Exposure to other conditions known to be potential risk factors for SIDS, such as but not limited to (this should be determined on a case by case basis taking into account the subject's entire medical history and environmental living conditions):

  • Mothers who smoked or abused drugs during pregnancy.
  • Extremely young mothers (defined as age 19 or younger when pregnant).
  • Children currently exposed to a caregiver which is a heavy cigarette smoker (defined as smoking at least a pack of cigarettes per day).
  • Babies who sleep regularly on their face or are not put to sleep on their backs.
  • Premature birth gestational age ≤ 37 weeks) or low birth weight (below 10 percentile for gestational age).