Povidone iodine (Betadine) allergy and radiocontrast hypersensitivity
Recently, I saw an elderly woman with concern for allergy to Betadine (and its relationship to IV contrast). She reports she had a local reaction to Betadine in 1998, and when it was used in 2006, she initially developed a local reaction but it progressed to affect most body surface areas including mucous membranes. Timeframe/other details are not known. Certainly, she was given other perioperative medications at the time, and these are unknown as well. It resolved eventually with po steroids, and she didn't require admission. From what I have read, this is extremely rare. My questions are 1. Is there any clear and safe way to test her for allergy to Betadine? 2. Is this related to IV contrast allergy?
Povidone iodine allergy is very rare but has been reported. Skin testing with undiluted (25mg/ml) solution has been reported but the predictive value of positive and negative testing is not defined (Gray). Other topical antiseptics, notably chlorhexidine, have also been associated with systemic reactions, particularly when applied to disrupted or injured epithelial surfaces. One report suggests that over 9% of perianesthetic anaphylaxis may be related to chlorhexidine sensitivity (Opstrup).
Iodine as an antigen or component of radiocontrast dyes is not related to radiocontrast reactions. Therefore, there is no relationship between radiocontrast sensitivity and povidone iodine.
In summary, povidone iodine is a rare cause of allergic or allergic-like reactions. Prick skin testing has been reported using a concentration of 25mg/ml (undiluted) [Gray]. Chlorhexidine may also cause systemic reactions, but there is no cross-reactivity between chlorhexidine and povidone iodine. Radio contrast reactions are not related to iodine allergy. There is no concern about possible cross-reactivity between radiocontrast and povidone iodine.
Recurrent anaphylaxis caused by topical povidone-iodine (Betadine). Gray PE, Katelaris CH, Lipson D. J Paediatr Child Health. 2013 Jun;49(6):506-7
Standardized testing with chlorhexidine in perioperative allergy--a large single-centre evaluation. Opstrup MS, Malling HJ, Krøigaard M, Mosbech H, Skov PS, Poulsen LK, Garvey LH Allergy. 2014;69(10):1390.
I hope this information is of help to you and your patient.
All my best.
Dennis K. Ledford, MD, FAAAAI