Antihistamines and skin testing
Question:
4/15/2020
Now that most of the oral antihistamine medications are over the counter, what is the new recommendation for a patient (number of days) to avoid antihistamines before their skin testing and challenges?
Answer:
Generally, one week for 2nd and 3rd generation antihistamine (cetirizine, loratadine, fexofenadine and levocetirizine and desloratadine). 48 hours is usually adequate for 1st generation (diphenhydramine and chlorpheniramine).
One recent study demonstrated that the wheal and flare responses returned to greater than 90% baseline within 4 days of not taking cetirizine. (1)
1) Shtessel M, Tversky J. Reliability of allergy skin testing. Ann Allergy Asthma Immunol. 2018;120(1):80–83.
Reference (2) is a good summary of the half-life of all the antihistamines and is Free Open Access through PubMed……..7 X half-life is typically considered adequate clearance from the body.
2) Maciel-Guerra H, Penha MÁ, Jorge MFS, et al. Suppression of wheal and flare in histamine test by the main H1 antihistamines commercialized in Brazil. An Bras Dermatol. 2018;93(2):233–237. doi:10.1590/abd1806-4841.20186807
I hope this is helpful.
Respectfully submitted,
Jeffrey G Demain, MD, FAAAAI