At what age can antihistamines (e.g. diphenhydramine) be safely administered to pediatric patients?

Age Guidelines for Starting Antihistamines in Pediatric Patients

Second-generation antihistamines (cetirizine, loratadine) can be safely started at 6 months of age, while first-generation antihistamines like diphenhydramine should be avoided in children under 6 years due to significant safety concerns including risk of fatalities. 1, 2

Age-Specific Antihistamine Recommendations

Infants Under 6 Months

• Antihistamines are not recommended in this age group due to lack of safety data and FDA approval 2
• Between 1969-2006, there were 41 fatalities associated with antihistamines in children under 2 years, highlighting the serious risks in young infants 1, 2
• For allergic symptoms in this age group, intranasal corticosteroids are the most effective first-line treatment, controlling all four major symptoms of allergic rhinitis 2

Infants 6-11 Months

• Cetirizine can be administered at 0.25 mg/kg twice daily (approximately 2.5 mg twice daily for a 10 kg infant) based on controlled safety studies 1, 2
• Loratadine has also been studied in controlled trials down to 6 months of age 1
• This represents the earliest age at which second-generation antihistamines have documented safety profiles 2

Children 2-5 Years

• Cetirizine: 2.5 mg once or twice daily (FDA-approved dosing) 1
• Loratadine: 5 mg once daily (FDA-approved dosing) 1, 3
• These are the only two antihistamines with FDA approval for children under 5 years 1
• Possible sedation may occur with higher than recommended doses, emphasizing the importance of adherence to proper dosing 1

Children 6 Years and Older

• Additional second-generation antihistamines become available, including desloratadine, fexofenadine, and levocetirizine 1
• Intranasal antihistamines (azelastine, olopatadine) are only approved for children 12 years and older 1

Critical Safety Considerations

First-Generation Antihistamines

• The FDA and American Academy of Pediatrics recommend against using first-generation antihistamines (diphenhydramine, chlorphenamine) in children under 6 years due to significant safety concerns 1
• These medications impair CNS function far more commonly than generally realized and should be restricted to two specific situations: severe pruritus requiring sedation, or anaphylaxis requiring intravenous diphenhydramine as adjunctive treatment to epinephrine 4
• In 2007, the FDA's advisory committees recommended that OTC cough and cold medications containing antihistamines no longer be used for children below 6 years of age 2

Special Clinical Scenarios

Anaphylaxis Exception:

• In anaphylaxis, diphenhydramine 1-2 mg/kg (25-50 mg per dose) can be administered parenterally as second-line therapy to epinephrine, never as monotherapy 5
• This represents the only appropriate use of first-generation antihistamines in young children 5, 4

Renal Impairment:

• Cetirizine requires dose reduction in moderate renal impairment and should be avoided in severe renal impairment 2
• This consideration applies once the child reaches appropriate age for antihistamine use 2

Common Pitfalls to Avoid

• Never use intranasal antihistamines in children under 6 years due to lack of FDA approval 1
• Avoid off-label prescribing in children under 2 years, where most safety data are lacking 6
• Do not use first-generation antihistamines for routine allergic symptoms in children under 6 years, despite their widespread historical use and presumed safety 1, 4
• Consult product labeling before prescribing in children under 6 years, as dosing and age restrictions vary significantly between products 2

Alternative Treatment Options for Young Children

When antihistamines are not appropriate or insufficient:

• Intranasal corticosteroids are the most effective medication class for allergic rhinitis in all pediatric age groups, with onset of action between 3-12 hours 1, 2
• Saline irrigation (isotonic or hypertonic) provides modest benefit with minimal side effects, low cost, and good patient acceptance 1, 2