Which oral antihistamine can be prescribed for a 20‑month‑old child?

Antihistamine Options for a 20-Month-Old Child

For a 20-month-old child requiring antihistamine therapy, cetirizine 0.25 mg/kg twice daily (approximately 2.5 mg twice daily for a typical 10 kg child) is the recommended oral antihistamine, as it is one of only two antihistamines with documented safety data and FDA approval for children under 2 years of age. 1, 2

FDA-Approved Options for This Age Group

• Cetirizine is the primary choice for infants 6-11 months and toddlers up to 2 years, with a proven safety profile in a randomized, double-blind, placebo-controlled study specifically conducted in infants 6-11 months of age 2
• The recommended dose is 0.25 mg/kg twice daily, which translates to approximately 2.5 mg twice daily for a typical 10 kg toddler 1
• Cetirizine and loratadine are the only two antihistamines with FDA approval for children under 5 years of age 1

Alternative Second-Generation Antihistamine

• Loratadine can be considered as an alternative, though it is typically dosed at 5 mg once daily for children aged 2-5 years 1, 3
• For a 20-month-old (just under 2 years), loratadine dosing would require physician consultation, as most approval extends down to age 2 years 1

Critical Safety Warnings: What to Avoid

• Never prescribe first-generation antihistamines (diphenhydramine, hydroxyzine) for routine allergic symptoms in children under 6 years due to significant safety concerns 1, 3
• Between 1969-2006, there were 69 fatalities associated with antihistamines in children under 6 years, with 41 deaths occurring in children under 2 years, and diphenhydramine was responsible for 33 of these deaths 1, 3
• The FDA and American Academy of Pediatrics explicitly recommend against using OTC cough and cold medications containing first-generation antihistamines in children below 6 years of age 1, 3
• Intranasal antihistamines (azelastine, olopatadine) are only approved for children 12 years and older and should not be used in this age group 4, 1

Preferred First-Line Treatment Alternative

• Intranasal corticosteroids are actually the most effective medication class for controlling all symptoms of allergic rhinitis in children under 2 years, with high-quality evidence supporting their use 1
• When given in recommended doses, intranasal corticosteroids are not associated with clinically significant systemic side effects 1
• Consider intranasal corticosteroids as first-line therapy, with cetirizine as second-line or adjunctive treatment 1

Practical Administration Considerations

• Liquid formulations are strongly preferred in young children for easier administration and better absorption 3
• Monitor for possible sedation with higher-than-usual doses of cetirizine, though this is uncommon at recommended dosing 1
• Second-generation antihistamines like cetirizine have been shown to be well-tolerated with excellent safety profiles in young children 1, 5, 6

Common Pitfall to Avoid

• Do not use antihistamines "to make a child sleepy"—this is explicitly contraindicated per FDA labeling 3
• Avoid OTC cough and cold combination products in children under 6 years due to overdose risk 3
• Oral decongestants (pseudoephedrine, phenylephrine) should be used with extreme caution in infants and young children, as use has been associated with agitated psychosis, ataxia, hallucinations, and even death 4