Rule #1
Antihistamines should only be used to treat allergic rhinitis, urticaria, and conjunctivitis.
Do NOT use for asthma, eczema, cough, or insomnia management.
Rule #2
Be mindful of the side-effect profile associated with first-generation antihistamines, including the anticholinergic and anti-alpha-adrenergic properties which can result in prolonged QT and death.
DO NOT use in elderly populations or with alcohol.
Rule #3
Stick to the approved list: Bilastine, Cetirizine, Desloratadine, Fexofenadine, Loratadine and Rupatadine. These newer antihistamines should be selected when available. Their heightened safety profile and increased duration and speed of action make them a much preferable choice.
Rule #4
DO NOT replace epinephrine with antihistamines in the treatment of anaphylaxis.
Antihistamines MAY be used in ADDITION but beware of hypotension.
Rule #5
Do not be afraid to use antihistamines in pregnant or breastfeeding women or children; they have been deemed safe in both these populations.
Inadequate evidence regarding rupatadine and bilastine
How to use antihistamines
CMAJ April 06, 2021 193 (14) E478-E479; DOI: https://doi.org/10.1503/cmaj.201959