From the Research
I do not recommend giving Allegra (fexofenadine) to a 6-month-old infant, as it is not FDA-approved for children under 2 years of age. For infants this young who may be experiencing allergy symptoms, you should consult with a pediatrician before giving any antihistamine medication. The doctor may recommend alternative treatments appropriate for the infant's age, weight, and specific symptoms. Antihistamines like Allegra work by blocking histamine receptors, which can help reduce allergy symptoms, but dosing for infants is particularly sensitive due to their developing organs and different metabolism rates compared to older children and adults.
Instead of medication, you might try to identify and remove allergens from the infant's environment, use a cool-mist humidifier, ensure proper hydration, and gently suction nasal mucus as needed. If your baby is showing signs of allergies such as a rash, congestion, or irritability, please contact your pediatrician for proper evaluation and age-appropriate treatment recommendations. None of the provided studies 1, 2, 3, 4, 5 discuss the use of fexofenadine in infants, and therefore, do not provide guidance on the recommended dose for a 6-month-old infant.